Volume Server: handle incomplete ec encoding (#7384)

* handle incomplete ec encoding

* unit tests

* simplify, and better logs

* Update disk_location_ec.go

When loadEcShards() fails partway through, some EC shards may already be loaded into the l.ecVolumes map in memory. The previous code only cleaned up filesystem files but left orphaned in-memory state, which could cause memory leaks and inconsistent state.

* address comments

* Performance: Avoid Double os.Stat() Call
* Platform Compatibility: Use filepath.Join

* in memory cleanup

* Update disk_location_ec.go

* refactor

* Added Shard Size Validation

* check ec shard sizes

* validate shard size

* calculate expected shard size

* refactoring

* minor

* fix shard directory

* 10GB sparse files can be slow or fail on non-sparse FS. Use 10MB to hit SmallBlockSize math (1MB shards) deterministically.

* grouping logic should be updated to use both collection and volumeId to ensure correctness

* unexpected error

* handle exceptions in tests; use constants

* The check for orphaned shards should be performed for the previous volume before resetting sameVolumeShards for the new volume.

* address comments

* Eliminated Redundant Parsing in checkOrphanedShards

* minor

* Avoid misclassifying local EC as distributed when .dat stat errors occur; also standardize unload-before-remove.

* fmt

* refactor

* refactor

* adjust to warning

5 files changed, 1301 insertions, 16 deletions

diff --git a/weed/storage/disk_location.go b/weed/storage/disk_location.go
index aac824318..e8c1d10e4 100644
--- a/weed/storage/disk_location.go
+++ b/weed/storage/disk_location.go
@@ -144,10 +144,26 @@ func (l *DiskLocation) loadExistingVolume(dirEntry os.DirEntry, needleMapKind Ne
 		return false
 	}
 
-	// skip if ec volumes exists
+	// parse out collection, volume id (moved up to use in EC validation)
+	vid, collection, err := volumeIdFromFileName(basename)
+	if err != nil {
+		glog.Warningf("get volume id failed, %s, err : %s", volumeName, err)
+		return false
+	}
+
+	// skip if ec volumes exists, but validate EC files first
 	if skipIfEcVolumesExists {
-		if util.FileExists(l.IdxDirectory + "/" + volumeName + ".ecx") {
-			return false
+		ecxFilePath := filepath.Join(l.IdxDirectory, volumeName+".ecx")
+		if util.FileExists(ecxFilePath) {
+			// Check if EC volume is valid by verifying shard count
+			if !l.validateEcVolume(collection, vid) {
+				glog.Warningf("EC volume %d validation failed, removing incomplete EC files to allow .dat file loading", vid)
+				l.removeEcVolumeFiles(collection, vid)
+				// Continue to load .dat file
+			} else {
+				// Valid EC volume exists, skip .dat file
+				return false
+			}
 		}
 	}
 
@@ -161,13 +177,6 @@ func (l *DiskLocation) loadExistingVolume(dirEntry os.DirEntry, needleMapKind Ne
 		return false
 	}
 
-	// parse out collection, volume id
-	vid, collection, err := volumeIdFromFileName(basename)
-	if err != nil {
-		glog.Warningf("get volume id failed, %s, err : %s", volumeName, err)
-		return false
-	}
-
 	// avoid loading one volume more than once
 	l.volumesLock.RLock()
 	_, found := l.volumes[vid]
diff --git a/weed/storage/disk_location_ec.go b/weed/storage/disk_location_ec.go
index 0db73adc6..128bfd26f 100644
--- a/weed/storage/disk_location_ec.go
+++ b/weed/storage/disk_location_ec.go
@@ -10,6 +10,7 @@ import (
 
 	"slices"
 
+	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
 	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
 )
@@ -40,6 +41,23 @@ func (l *DiskLocation) DestroyEcVolume(vid needle.VolumeId) {
 	}
 }
 
+// unloadEcVolume removes an EC volume from memory without deleting its files on disk.
+// This is useful for distributed EC volumes where shards may be on other servers.
+func (l *DiskLocation) unloadEcVolume(vid needle.VolumeId) {
+	var toClose *erasure_coding.EcVolume
+	l.ecVolumesLock.Lock()
+	if ecVolume, found := l.ecVolumes[vid]; found {
+		toClose = ecVolume
+		delete(l.ecVolumes, vid)
+	}
+	l.ecVolumesLock.Unlock()
+
+	// Close outside the lock to avoid holding write lock during I/O
+	if toClose != nil {
+		toClose.Close()
+	}
+}
+
 func (l *DiskLocation) CollectEcShards(vid needle.VolumeId, shardFileNames []string) (ecVolume *erasure_coding.EcVolume, found bool) {
 	l.ecVolumesLock.RLock()
 	defer l.ecVolumesLock.RUnlock()
@@ -154,8 +172,18 @@ func (l *DiskLocation) loadAllEcShards() (err error) {
 	slices.SortFunc(dirEntries, func(a, b os.DirEntry) int {
 		return strings.Compare(a.Name(), b.Name())
 	})
+
 	var sameVolumeShards []string
 	var prevVolumeId needle.VolumeId
+	var prevCollection string
+
+	// Helper to reset state between volume processing
+	reset := func() {
+		sameVolumeShards = nil
+		prevVolumeId = 0
+		prevCollection = ""
+	}
+
 	for _, fileInfo := range dirEntries {
 		if fileInfo.IsDir() {
 			continue
@@ -178,24 +206,31 @@ func (l *DiskLocation) loadAllEcShards() (err error) {
 		// 0 byte files should be only appearing erroneously for ec data files
 		// so we ignore them
 		if re.MatchString(ext) && info.Size() > 0 {
-			if prevVolumeId == 0 || volumeId == prevVolumeId {
+			// Group shards by both collection and volumeId to avoid mixing collections
+			if prevVolumeId == 0 || (volumeId == prevVolumeId && collection == prevCollection) {
 				sameVolumeShards = append(sameVolumeShards, fileInfo.Name())
 			} else {
+				// Before starting a new group, check if previous group had orphaned shards
+				l.checkOrphanedShards(sameVolumeShards, prevCollection, prevVolumeId)
 				sameVolumeShards = []string{fileInfo.Name()}
 			}
 			prevVolumeId = volumeId
+			prevCollection = collection
 			continue
 		}
 
-		if ext == ".ecx" && volumeId == prevVolumeId {
-			if err = l.loadEcShards(sameVolumeShards, collection, volumeId); err != nil {
-				return fmt.Errorf("loadEcShards collection:%v volumeId:%d : %v", collection, volumeId, err)
-			}
-			prevVolumeId = volumeId
+		if ext == ".ecx" && volumeId == prevVolumeId && collection == prevCollection {
+			l.handleFoundEcxFile(sameVolumeShards, collection, volumeId)
+			reset()
 			continue
 		}
 
 	}
+
+	// Check for orphaned EC shards without .ecx file at the end of the directory scan
+	// This handles the last group of shards in the directory
+	l.checkOrphanedShards(sameVolumeShards, prevCollection, prevVolumeId)
+
 	return nil
 }
 
@@ -237,3 +272,208 @@ func (l *DiskLocation) EcShardCount() int {
 	}
 	return shardCount
 }
+
+// handleFoundEcxFile processes a complete group of EC shards when their .ecx file is found.
+// This includes validation, loading, and cleanup of incomplete/invalid EC volumes.
+func (l *DiskLocation) handleFoundEcxFile(shards []string, collection string, volumeId needle.VolumeId) {
+	// Check if this is an incomplete EC encoding (not a distributed EC volume)
+	// Key distinction: if .dat file still exists, EC encoding may have failed
+	// If .dat file is gone, this is likely a distributed EC volume with shards on multiple servers
+	baseFileName := erasure_coding.EcShardFileName(collection, l.Directory, int(volumeId))
+	datFileName := baseFileName + ".dat"
+
+	// Determine .dat presence robustly; unexpected errors are treated as "exists"
+	datExists := l.checkDatFileExists(datFileName)
+
+	// Validate EC volume if .dat file exists (incomplete EC encoding scenario)
+	// This checks shard count, shard size consistency, and expected size vs .dat file
+	// If .dat is gone, EC encoding completed and shards are distributed across servers
+	if datExists && !l.validateEcVolume(collection, volumeId) {
+		glog.Warningf("Incomplete or invalid EC volume %d: .dat exists but validation failed, cleaning up EC files...", volumeId)
+		l.removeEcVolumeFiles(collection, volumeId)
+		return
+	}
+
+	// Attempt to load the EC shards
+	if err := l.loadEcShards(shards, collection, volumeId); err != nil {
+		// If EC shards failed to load and .dat still exists, clean up EC files to allow .dat file to be used
+		// If .dat is gone, log error but don't clean up (may be waiting for shards from other servers)
+		if datExists {
+			glog.Warningf("Failed to load EC shards for volume %d and .dat exists: %v, cleaning up EC files to use .dat...", volumeId, err)
+			// Unload first to release FDs, then remove files
+			l.unloadEcVolume(volumeId)
+			l.removeEcVolumeFiles(collection, volumeId)
+		} else {
+			glog.Warningf("Failed to load EC shards for volume %d: %v (this may be normal for distributed EC volumes)", volumeId, err)
+			// Clean up any partially loaded in-memory state. This does not delete files.
+			l.unloadEcVolume(volumeId)
+		}
+		return
+	}
+}
+
+// checkDatFileExists checks if .dat file exists with robust error handling.
+// Unexpected errors (permission, I/O) are treated as "exists" to avoid misclassifying
+// local EC as distributed EC, which is the safer fallback.
+func (l *DiskLocation) checkDatFileExists(datFileName string) bool {
+	if _, err := os.Stat(datFileName); err == nil {
+		return true
+	} else if !os.IsNotExist(err) {
+		glog.Warningf("Failed to stat .dat file %s: %v", datFileName, err)
+		// Safer to assume local .dat exists to avoid misclassifying as distributed EC
+		return true
+	}
+	return false
+}
+
+// checkOrphanedShards checks if the given shards are orphaned (no .ecx file) and cleans them up if needed.
+// Returns true if orphaned shards were found and cleaned up.
+// This handles the case where EC encoding was interrupted before creating the .ecx file.
+func (l *DiskLocation) checkOrphanedShards(shards []string, collection string, volumeId needle.VolumeId) bool {
+	if len(shards) == 0 || volumeId == 0 {
+		return false
+	}
+
+	// Check if .dat file exists (incomplete encoding, not distributed EC)
+	baseFileName := erasure_coding.EcShardFileName(collection, l.Directory, int(volumeId))
+	datFileName := baseFileName + ".dat"
+
+	if l.checkDatFileExists(datFileName) {
+		glog.Warningf("Found %d EC shards without .ecx file for volume %d (incomplete encoding interrupted before .ecx creation), cleaning up...",
+			len(shards), volumeId)
+		l.removeEcVolumeFiles(collection, volumeId)
+		return true
+	}
+	return false
+}
+
+// calculateExpectedShardSize computes the exact expected shard size based on .dat file size
+// The EC encoding process is deterministic:
+// 1. Data is processed in batches of (LargeBlockSize * DataShardsCount) for large blocks
+// 2. Remaining data is processed in batches of (SmallBlockSize * DataShardsCount) for small blocks
+// 3. Each shard gets exactly its portion, with zero-padding applied to incomplete blocks
+func calculateExpectedShardSize(datFileSize int64) int64 {
+	var shardSize int64
+
+	// Process large blocks (1GB * 10 = 10GB batches)
+	largeBatchSize := int64(erasure_coding.ErasureCodingLargeBlockSize) * int64(erasure_coding.DataShardsCount)
+	numLargeBatches := datFileSize / largeBatchSize
+	shardSize = numLargeBatches * int64(erasure_coding.ErasureCodingLargeBlockSize)
+	remainingSize := datFileSize - (numLargeBatches * largeBatchSize)
+
+	// Process remaining data in small blocks (1MB * 10 = 10MB batches)
+	if remainingSize > 0 {
+		smallBatchSize := int64(erasure_coding.ErasureCodingSmallBlockSize) * int64(erasure_coding.DataShardsCount)
+		numSmallBatches := (remainingSize + smallBatchSize - 1) / smallBatchSize // Ceiling division
+		shardSize += numSmallBatches * int64(erasure_coding.ErasureCodingSmallBlockSize)
+	}
+
+	return shardSize
+}
+
+// validateEcVolume checks if EC volume has enough shards to be functional
+// For distributed EC volumes (where .dat is deleted), any number of shards is valid
+// For incomplete EC encoding (where .dat still exists), we need at least DataShardsCount shards
+// Also validates that all shards have the same size (required for Reed-Solomon EC)
+// If .dat exists, it also validates shards match the expected size based on .dat file size
+func (l *DiskLocation) validateEcVolume(collection string, vid needle.VolumeId) bool {
+	baseFileName := erasure_coding.EcShardFileName(collection, l.Directory, int(vid))
+	datFileName := baseFileName + ".dat"
+
+	var expectedShardSize int64 = -1
+	datExists := false
+
+	// If .dat file exists, compute exact expected shard size from it
+	if datFileInfo, err := os.Stat(datFileName); err == nil {
+		datExists = true
+		expectedShardSize = calculateExpectedShardSize(datFileInfo.Size())
+	} else if !os.IsNotExist(err) {
+		// If stat fails with unexpected error (permission, I/O), fail validation
+		// Don't treat this as "distributed EC" - it could be a temporary error
+		glog.Warningf("Failed to stat .dat file %s: %v", datFileName, err)
+		return false
+	}
+
+	shardCount := 0
+	var actualShardSize int64 = -1
+
+	// Count shards and validate they all have the same size (required for Reed-Solomon EC)
+	// Shard files (.ec00 - .ec13) are always in l.Directory, not l.IdxDirectory
+	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+		shardFileName := baseFileName + erasure_coding.ToExt(i)
+		fi, err := os.Stat(shardFileName)
+
+		if err == nil {
+			// Check if file has non-zero size
+			if fi.Size() > 0 {
+				// Validate all shards are the same size (required for Reed-Solomon EC)
+				if actualShardSize == -1 {
+					actualShardSize = fi.Size()
+				} else if fi.Size() != actualShardSize {
+					glog.Warningf("EC volume %d shard %d has size %d, expected %d (all EC shards must be same size)",
+						vid, i, fi.Size(), actualShardSize)
+					return false
+				}
+				shardCount++
+			}
+		} else if !os.IsNotExist(err) {
+			// If stat fails with unexpected error (permission, I/O), fail validation
+			// This is consistent with .dat file error handling
+			glog.Warningf("Failed to stat shard file %s: %v", shardFileName, err)
+			return false
+		}
+	}
+
+	// If .dat file exists, validate shard size matches expected size
+	if datExists && actualShardSize > 0 && expectedShardSize > 0 {
+		if actualShardSize != expectedShardSize {
+			glog.Warningf("EC volume %d: shard size %d doesn't match expected size %d (based on .dat file size)",
+				vid, actualShardSize, expectedShardSize)
+			return false
+		}
+	}
+
+	// If .dat file is gone, this is a distributed EC volume - any shard count is valid
+	if !datExists {
+		glog.V(1).Infof("EC volume %d: distributed EC (.dat removed) with %d shards", vid, shardCount)
+		return true
+	}
+
+	// If .dat file exists, we need at least DataShardsCount shards locally
+	// Otherwise it's an incomplete EC encoding that should be cleaned up
+	if shardCount < erasure_coding.DataShardsCount {
+		glog.Warningf("EC volume %d has .dat file but only %d shards (need at least %d for local EC)",
+			vid, shardCount, erasure_coding.DataShardsCount)
+		return false
+	}
+
+	return true
+}
+
+// removeEcVolumeFiles removes all EC-related files for a volume
+func (l *DiskLocation) removeEcVolumeFiles(collection string, vid needle.VolumeId) {
+	baseFileName := erasure_coding.EcShardFileName(collection, l.Directory, int(vid))
+	indexBaseFileName := erasure_coding.EcShardFileName(collection, l.IdxDirectory, int(vid))
+
+	// Helper to remove a file with consistent error handling
+	removeFile := func(filePath, description string) {
+		if err := os.Remove(filePath); err != nil {
+			if !os.IsNotExist(err) {
+				glog.Warningf("Failed to remove incomplete %s %s: %v", description, filePath, err)
+			}
+		} else {
+			glog.V(2).Infof("Removed incomplete %s: %s", description, filePath)
+		}
+	}
+
+	// Remove index files first (.ecx, .ecj) before shard files
+	// This ensures that if cleanup is interrupted, the .ecx file won't trigger
+	// EC loading for incomplete/missing shards on next startup
+	removeFile(indexBaseFileName+".ecx", "EC index file")
+	removeFile(indexBaseFileName+".ecj", "EC journal file")
+
+	// Remove all EC shard files (.ec00 ~ .ec13) from data directory
+	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+		removeFile(baseFileName+erasure_coding.ToExt(i), "EC shard file")
+	}
+}
diff --git a/weed/storage/disk_location_ec_realworld_test.go b/weed/storage/disk_location_ec_realworld_test.go
new file mode 100644
index 000000000..3a21ccb6c
--- /dev/null
+++ b/weed/storage/disk_location_ec_realworld_test.go
@@ -0,0 +1,198 @@
+package storage
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
+)
+
+// TestCalculateExpectedShardSizeWithRealEncoding validates our shard size calculation
+// by actually running EC encoding on real files and comparing the results
+func TestCalculateExpectedShardSizeWithRealEncoding(t *testing.T) {
+	tempDir := t.TempDir()
+
+	tests := []struct {
+		name        string
+		datFileSize int64
+		description string
+	}{
+		{
+			name:        "5MB file",
+			datFileSize: 5 * 1024 * 1024,
+			description: "Small file that needs 1 small block per shard",
+		},
+		{
+			name:        "10MB file (exactly 10 small blocks)",
+			datFileSize: 10 * 1024 * 1024,
+			description: "Exactly fits in 1MB small blocks",
+		},
+		{
+			name:        "15MB file",
+			datFileSize: 15 * 1024 * 1024,
+			description: "Requires 2 small blocks per shard",
+		},
+		{
+			name:        "50MB file",
+			datFileSize: 50 * 1024 * 1024,
+			description: "Requires 5 small blocks per shard",
+		},
+		{
+			name:        "100MB file",
+			datFileSize: 100 * 1024 * 1024,
+			description: "Requires 10 small blocks per shard",
+		},
+		{
+			name:        "512MB file",
+			datFileSize: 512 * 1024 * 1024,
+			description: "Requires 52 small blocks per shard (rounded up)",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create a test .dat file with the specified size
+			baseFileName := filepath.Join(tempDir, "test_volume")
+			datFileName := baseFileName + ".dat"
+
+			// Create .dat file with random data pattern (so it's compressible but realistic)
+			datFile, err := os.Create(datFileName)
+			if err != nil {
+				t.Fatalf("Failed to create .dat file: %v", err)
+			}
+
+			// Write some pattern data (not all zeros, to be more realistic)
+			pattern := make([]byte, 4096)
+			for i := range pattern {
+				pattern[i] = byte(i % 256)
+			}
+
+			written := int64(0)
+			for written < tt.datFileSize {
+				toWrite := tt.datFileSize - written
+				if toWrite > int64(len(pattern)) {
+					toWrite = int64(len(pattern))
+				}
+				n, err := datFile.Write(pattern[:toWrite])
+				if err != nil {
+					t.Fatalf("Failed to write to .dat file: %v", err)
+				}
+				written += int64(n)
+			}
+			datFile.Close()
+
+			// Calculate expected shard size using our function
+			expectedShardSize := calculateExpectedShardSize(tt.datFileSize)
+
+			// Run actual EC encoding
+			err = erasure_coding.WriteEcFiles(baseFileName)
+			if err != nil {
+				t.Fatalf("Failed to encode EC files: %v", err)
+			}
+
+			// Measure actual shard sizes
+			for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+				shardFileName := baseFileName + erasure_coding.ToExt(i)
+				shardInfo, err := os.Stat(shardFileName)
+				if err != nil {
+					t.Fatalf("Failed to stat shard file %s: %v", shardFileName, err)
+				}
+
+				actualShardSize := shardInfo.Size()
+
+				// Verify actual size matches expected size
+				if actualShardSize != expectedShardSize {
+					t.Errorf("Shard %d size mismatch:\n"+
+						"  .dat file size: %d bytes\n"+
+						"  Expected shard size: %d bytes\n"+
+						"  Actual shard size: %d bytes\n"+
+						"  Difference: %d bytes\n"+
+						"  %s",
+						i, tt.datFileSize, expectedShardSize, actualShardSize,
+						actualShardSize-expectedShardSize, tt.description)
+				}
+			}
+
+			// If we got here, all shards match!
+			t.Logf("✓ SUCCESS: .dat size %d → actual shard size %d matches calculated size (%s)",
+				tt.datFileSize, expectedShardSize, tt.description)
+
+			// Cleanup
+			os.Remove(datFileName)
+			for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+				os.Remove(baseFileName + erasure_coding.ToExt(i))
+			}
+		})
+	}
+}
+
+// TestCalculateExpectedShardSizeEdgeCases tests edge cases with real encoding
+func TestCalculateExpectedShardSizeEdgeCases(t *testing.T) {
+	tempDir := t.TempDir()
+
+	tests := []struct {
+		name        string
+		datFileSize int64
+	}{
+		{"1 byte file", 1},
+		{"1KB file", 1024},
+		{"10KB file", 10 * 1024},
+		{"1MB file (1 small block)", 1024 * 1024},
+		{"1MB + 1 byte", 1024*1024 + 1},
+		{"9.9MB (almost 1 small block per shard)", 9*1024*1024 + 900*1024},
+		{"10.1MB (just over 1 small block per shard)", 10*1024*1024 + 100*1024},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			baseFileName := filepath.Join(tempDir, tt.name)
+			datFileName := baseFileName + ".dat"
+
+			// Create .dat file
+			datFile, err := os.Create(datFileName)
+			if err != nil {
+				t.Fatalf("Failed to create .dat file: %v", err)
+			}
+
+			// Write exactly the specified number of bytes
+			data := make([]byte, tt.datFileSize)
+			for i := range data {
+				data[i] = byte(i % 256)
+			}
+			datFile.Write(data)
+			datFile.Close()
+
+			// Calculate expected
+			expectedShardSize := calculateExpectedShardSize(tt.datFileSize)
+
+			// Run actual EC encoding
+			err = erasure_coding.WriteEcFiles(baseFileName)
+			if err != nil {
+				t.Fatalf("Failed to encode EC files: %v", err)
+			}
+
+			// Check first shard (all should be same size)
+			shardFileName := baseFileName + erasure_coding.ToExt(0)
+			shardInfo, err := os.Stat(shardFileName)
+			if err != nil {
+				t.Fatalf("Failed to stat shard file: %v", err)
+			}
+
+			actualShardSize := shardInfo.Size()
+
+			if actualShardSize != expectedShardSize {
+				t.Errorf("File size %d: expected shard %d, got %d (diff: %d)",
+					tt.datFileSize, expectedShardSize, actualShardSize, actualShardSize-expectedShardSize)
+			} else {
+				t.Logf("✓ File size %d → shard size %d (correct)", tt.datFileSize, actualShardSize)
+			}
+
+			// Cleanup
+			os.Remove(datFileName)
+			for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+				os.Remove(baseFileName + erasure_coding.ToExt(i))
+			}
+		})
+	}
+}
diff --git a/weed/storage/disk_location_ec_shard_size_test.go b/weed/storage/disk_location_ec_shard_size_test.go
new file mode 100644
index 000000000..e58c1c129
--- /dev/null
+++ b/weed/storage/disk_location_ec_shard_size_test.go
@@ -0,0 +1,195 @@
+package storage
+
+import (
+	"testing"
+)
+
+func TestCalculateExpectedShardSize(t *testing.T) {
+	const (
+		largeBlock     = 1024 * 1024 * 1024 // 1GB
+		smallBlock     = 1024 * 1024        // 1MB
+		dataShards     = 10
+		largeBatchSize = largeBlock * dataShards // 10GB
+		smallBatchSize = smallBlock * dataShards // 10MB
+	)
+
+	tests := []struct {
+		name              string
+		datFileSize       int64
+		expectedShardSize int64
+		description       string
+	}{
+		// Edge case: empty file
+		{
+			name:              "0 bytes (empty file)",
+			datFileSize:       0,
+			expectedShardSize: 0,
+			description:       "Empty file has 0 shard size",
+		},
+
+		// Boundary tests: exact multiples of large block
+		{
+			name:              "Exact 10GB (1 large batch)",
+			datFileSize:       largeBatchSize, // 10GB = 1 large batch
+			expectedShardSize: largeBlock,     // 1GB per shard
+			description:       "Exactly fits in large blocks",
+		},
+		{
+			name:              "Exact 20GB (2 large batches)",
+			datFileSize:       2 * largeBatchSize, // 20GB
+			expectedShardSize: 2 * largeBlock,     // 2GB per shard
+			description:       "2 complete large batches",
+		},
+		{
+			name:              "Just under large batch (10GB - 1 byte)",
+			datFileSize:       largeBatchSize - 1, // 10,737,418,239 bytes
+			expectedShardSize: 1024 * smallBlock,  // 1024MB = 1GB (needs 1024 small blocks)
+			description:       "Just under 10GB needs 1024 small blocks",
+		},
+		{
+			name:              "Just over large batch (10GB + 1 byte)",
+			datFileSize:       largeBatchSize + 1,      // 10GB + 1 byte
+			expectedShardSize: largeBlock + smallBlock, // 1GB + 1MB
+			description:       "Just over 10GB adds 1 small block",
+		},
+
+		// Boundary tests: exact multiples of small batch
+		{
+			name:              "Exact 10MB (1 small batch)",
+			datFileSize:       smallBatchSize, // 10MB
+			expectedShardSize: smallBlock,     // 1MB per shard
+			description:       "Exactly fits in 1 small batch",
+		},
+		{
+			name:              "Exact 20MB (2 small batches)",
+			datFileSize:       2 * smallBatchSize, // 20MB
+			expectedShardSize: 2 * smallBlock,     // 2MB per shard
+			description:       "2 complete small batches",
+		},
+		{
+			name:              "Just under small batch (10MB - 1 byte)",
+			datFileSize:       smallBatchSize - 1, // 10MB - 1 byte
+			expectedShardSize: smallBlock,         // Still needs 1MB per shard (rounds up)
+			description:       "Just under 10MB rounds up to 1 small block",
+		},
+		{
+			name:              "Just over small batch (10MB + 1 byte)",
+			datFileSize:       smallBatchSize + 1, // 10MB + 1 byte
+			expectedShardSize: 2 * smallBlock,     // 2MB per shard
+			description:       "Just over 10MB needs 2 small blocks",
+		},
+
+		// Mixed: large batch + partial small batch
+		{
+			name:              "10GB + 1MB",
+			datFileSize:       largeBatchSize + 1*1024*1024, // 10GB + 1MB
+			expectedShardSize: largeBlock + smallBlock,      // 1GB + 1MB
+			description:       "1 large batch + 1MB needs 1 small block",
+		},
+		{
+			name:              "10GB + 5MB",
+			datFileSize:       largeBatchSize + 5*1024*1024, // 10GB + 5MB
+			expectedShardSize: largeBlock + smallBlock,      // 1GB + 1MB
+			description:       "1 large batch + 5MB rounds up to 1 small block",
+		},
+		{
+			name:              "10GB + 15MB",
+			datFileSize:       largeBatchSize + 15*1024*1024, // 10GB + 15MB
+			expectedShardSize: largeBlock + 2*smallBlock,     // 1GB + 2MB
+			description:       "1 large batch + 15MB needs 2 small blocks",
+		},
+
+		// Original test cases
+		{
+			name:              "11GB (1 large batch + 103 small blocks)",
+			datFileSize:       11 * 1024 * 1024 * 1024,          // 11GB
+			expectedShardSize: 1*1024*1024*1024 + 103*1024*1024, // 1GB + 103MB (103 small blocks for 1GB remaining)
+			description:       "1GB large + 1GB remaining needs 103 small blocks",
+		},
+		{
+			name:              "5MB (requires 1 small block per shard)",
+			datFileSize:       5 * 1024 * 1024, // 5MB
+			expectedShardSize: 1 * 1024 * 1024, // 1MB per shard (rounded up)
+			description:       "Small file rounds up to 1MB per shard",
+		},
+		{
+			name:              "1KB (minimum size)",
+			datFileSize:       1024,
+			expectedShardSize: 1 * 1024 * 1024, // 1MB per shard (1 small block)
+			description:       "Tiny file needs 1 small block",
+		},
+		{
+			name:              "10.5GB (mixed)",
+			datFileSize:       10*1024*1024*1024 + 512*1024*1024, // 10.5GB
+			expectedShardSize: 1*1024*1024*1024 + 52*1024*1024,   // 1GB + 52MB (52 small blocks for 512MB remaining)
+			description:       "1GB large + 512MB remaining needs 52 small blocks",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			actualShardSize := calculateExpectedShardSize(tt.datFileSize)
+
+			if actualShardSize != tt.expectedShardSize {
+				t.Errorf("Expected shard size %d, got %d. %s",
+					tt.expectedShardSize, actualShardSize, tt.description)
+			}
+
+			t.Logf("✓ File size: %d → Shard size: %d (%s)",
+				tt.datFileSize, actualShardSize, tt.description)
+		})
+	}
+}
+
+// TestShardSizeValidationScenarios tests realistic scenarios
+func TestShardSizeValidationScenarios(t *testing.T) {
+	scenarios := []struct {
+		name            string
+		datFileSize     int64
+		actualShardSize int64
+		shouldBeValid   bool
+	}{
+		{
+			name:            "Valid: exact match for 10GB",
+			datFileSize:     10 * 1024 * 1024 * 1024, // 10GB
+			actualShardSize: 1 * 1024 * 1024 * 1024,  // 1GB (exact)
+			shouldBeValid:   true,
+		},
+		{
+			name:            "Invalid: 1 byte too small",
+			datFileSize:     10 * 1024 * 1024 * 1024, // 10GB
+			actualShardSize: 1*1024*1024*1024 - 1,    // 1GB - 1 byte
+			shouldBeValid:   false,
+		},
+		{
+			name:            "Invalid: 1 byte too large",
+			datFileSize:     10 * 1024 * 1024 * 1024, // 10GB
+			actualShardSize: 1*1024*1024*1024 + 1,    // 1GB + 1 byte
+			shouldBeValid:   false,
+		},
+		{
+			name:            "Valid: small file exact match",
+			datFileSize:     5 * 1024 * 1024, // 5MB
+			actualShardSize: 1 * 1024 * 1024, // 1MB (exact)
+			shouldBeValid:   true,
+		},
+		{
+			name:            "Invalid: wrong size for small file",
+			datFileSize:     5 * 1024 * 1024, // 5MB
+			actualShardSize: 500 * 1024,      // 500KB (too small)
+			shouldBeValid:   false,
+		},
+	}
+
+	for _, scenario := range scenarios {
+		t.Run(scenario.name, func(t *testing.T) {
+			expectedSize := calculateExpectedShardSize(scenario.datFileSize)
+			isValid := scenario.actualShardSize == expectedSize
+
+			if isValid != scenario.shouldBeValid {
+				t.Errorf("Expected validation result %v, got %v. Actual shard: %d, Expected: %d",
+					scenario.shouldBeValid, isValid, scenario.actualShardSize, expectedSize)
+			}
+		})
+	}
+}
diff --git a/weed/storage/disk_location_ec_test.go b/weed/storage/disk_location_ec_test.go
new file mode 100644
index 000000000..097536118
--- /dev/null
+++ b/weed/storage/disk_location_ec_test.go
@@ -0,0 +1,643 @@
+package storage
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
+	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
+	"github.com/seaweedfs/seaweedfs/weed/storage/types"
+	"github.com/seaweedfs/seaweedfs/weed/util"
+)
+
+// TestIncompleteEcEncodingCleanup tests the cleanup logic for incomplete EC encoding scenarios
+func TestIncompleteEcEncodingCleanup(t *testing.T) {
+	tests := []struct {
+		name              string
+		volumeId          needle.VolumeId
+		collection        string
+		createDatFile     bool
+		createEcxFile     bool
+		createEcjFile     bool
+		numShards         int
+		expectCleanup     bool
+		expectLoadSuccess bool
+	}{
+		{
+			name:              "Incomplete EC: shards without .ecx, .dat exists - should cleanup",
+			volumeId:          100,
+			collection:        "",
+			createDatFile:     true,
+			createEcxFile:     false,
+			createEcjFile:     false,
+			numShards:         14, // All shards but no .ecx
+			expectCleanup:     true,
+			expectLoadSuccess: false,
+		},
+		{
+			name:              "Distributed EC: shards without .ecx, .dat deleted - should NOT cleanup",
+			volumeId:          101,
+			collection:        "",
+			createDatFile:     false,
+			createEcxFile:     false,
+			createEcjFile:     false,
+			numShards:         5, // Partial shards, distributed
+			expectCleanup:     false,
+			expectLoadSuccess: false,
+		},
+		{
+			name:              "Incomplete EC: shards with .ecx but < 10 shards, .dat exists - should cleanup",
+			volumeId:          102,
+			collection:        "",
+			createDatFile:     true,
+			createEcxFile:     true,
+			createEcjFile:     false,
+			numShards:         7, // Less than DataShardsCount (10)
+			expectCleanup:     true,
+			expectLoadSuccess: false,
+		},
+		{
+			name:              "Valid local EC: shards with .ecx, >= 10 shards, .dat exists - should load",
+			volumeId:          103,
+			collection:        "",
+			createDatFile:     true,
+			createEcxFile:     true,
+			createEcjFile:     false,
+			numShards:         14, // All shards
+			expectCleanup:     false,
+			expectLoadSuccess: true, // Would succeed if .ecx was valid
+		},
+		{
+			name:              "Distributed EC: shards with .ecx, .dat deleted - should load",
+			volumeId:          104,
+			collection:        "",
+			createDatFile:     false,
+			createEcxFile:     true,
+			createEcjFile:     false,
+			numShards:         10, // Enough shards
+			expectCleanup:     false,
+			expectLoadSuccess: true, // Would succeed if .ecx was valid
+		},
+		{
+			name:              "Incomplete EC with collection: shards without .ecx, .dat exists - should cleanup",
+			volumeId:          105,
+			collection:        "test_collection",
+			createDatFile:     true,
+			createEcxFile:     false,
+			createEcjFile:     false,
+			numShards:         14,
+			expectCleanup:     true,
+			expectLoadSuccess: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Use per-subtest temp directory for stronger isolation
+			tempDir := t.TempDir()
+
+			// Create DiskLocation
+			minFreeSpace := util.MinFreeSpace{Type: util.AsPercent, Percent: 1, Raw: "1"}
+			diskLocation := &DiskLocation{
+				Directory:              tempDir,
+				DirectoryUuid:          "test-uuid",
+				IdxDirectory:           tempDir,
+				DiskType:               types.HddType,
+				MaxVolumeCount:         100,
+				OriginalMaxVolumeCount: 100,
+				MinFreeSpace:           minFreeSpace,
+			}
+			diskLocation.volumes = make(map[needle.VolumeId]*Volume)
+			diskLocation.ecVolumes = make(map[needle.VolumeId]*erasure_coding.EcVolume)
+
+			// Setup test files
+			baseFileName := erasure_coding.EcShardFileName(tt.collection, tempDir, int(tt.volumeId))
+
+			// Use deterministic but small size: 10MB .dat => 1MB per shard
+			datFileSize := int64(10 * 1024 * 1024) // 10MB
+			expectedShardSize := calculateExpectedShardSize(datFileSize)
+
+			// Create .dat file if needed
+			if tt.createDatFile {
+				datFile, err := os.Create(baseFileName + ".dat")
+				if err != nil {
+					t.Fatalf("Failed to create .dat file: %v", err)
+				}
+				if err := datFile.Truncate(datFileSize); err != nil {
+					t.Fatalf("Failed to truncate .dat file: %v", err)
+				}
+				if err := datFile.Close(); err != nil {
+					t.Fatalf("Failed to close .dat file: %v", err)
+				}
+			}
+
+			// Create EC shard files
+			for i := 0; i < tt.numShards; i++ {
+				shardFile, err := os.Create(baseFileName + erasure_coding.ToExt(i))
+				if err != nil {
+					t.Fatalf("Failed to create shard file: %v", err)
+				}
+				if err := shardFile.Truncate(expectedShardSize); err != nil {
+					t.Fatalf("Failed to truncate shard file: %v", err)
+				}
+				if err := shardFile.Close(); err != nil {
+					t.Fatalf("Failed to close shard file: %v", err)
+				}
+			}
+
+			// Create .ecx file if needed
+			if tt.createEcxFile {
+				ecxFile, err := os.Create(baseFileName + ".ecx")
+				if err != nil {
+					t.Fatalf("Failed to create .ecx file: %v", err)
+				}
+				if _, err := ecxFile.WriteString("dummy ecx data"); err != nil {
+					ecxFile.Close()
+					t.Fatalf("Failed to write .ecx file: %v", err)
+				}
+				if err := ecxFile.Close(); err != nil {
+					t.Fatalf("Failed to close .ecx file: %v", err)
+				}
+			}
+
+			// Create .ecj file if needed
+			if tt.createEcjFile {
+				ecjFile, err := os.Create(baseFileName + ".ecj")
+				if err != nil {
+					t.Fatalf("Failed to create .ecj file: %v", err)
+				}
+				if _, err := ecjFile.WriteString("dummy ecj data"); err != nil {
+					ecjFile.Close()
+					t.Fatalf("Failed to write .ecj file: %v", err)
+				}
+				if err := ecjFile.Close(); err != nil {
+					t.Fatalf("Failed to close .ecj file: %v", err)
+				}
+			}
+
+			// Run loadAllEcShards
+			loadErr := diskLocation.loadAllEcShards()
+			if loadErr != nil {
+				t.Logf("loadAllEcShards returned error (expected in some cases): %v", loadErr)
+			}
+
+			// Test idempotency - running again should not cause issues
+			loadErr2 := diskLocation.loadAllEcShards()
+			if loadErr2 != nil {
+				t.Logf("Second loadAllEcShards returned error: %v", loadErr2)
+			}
+
+			// Verify cleanup expectations
+			if tt.expectCleanup {
+				// Check that files were cleaned up
+				if util.FileExists(baseFileName + ".ecx") {
+					t.Errorf("Expected .ecx to be cleaned up but it still exists")
+				}
+				if util.FileExists(baseFileName + ".ecj") {
+					t.Errorf("Expected .ecj to be cleaned up but it still exists")
+				}
+				for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+					shardFile := baseFileName + erasure_coding.ToExt(i)
+					if util.FileExists(shardFile) {
+						t.Errorf("Expected shard %d to be cleaned up but it still exists", i)
+					}
+				}
+				// .dat file should still exist (not cleaned up)
+				if tt.createDatFile && !util.FileExists(baseFileName+".dat") {
+					t.Errorf("Expected .dat file to remain but it was deleted")
+				}
+			} else {
+				// Check that files were NOT cleaned up
+				for i := 0; i < tt.numShards; i++ {
+					shardFile := baseFileName + erasure_coding.ToExt(i)
+					if !util.FileExists(shardFile) {
+						t.Errorf("Expected shard %d to remain but it was cleaned up", i)
+					}
+				}
+				if tt.createEcxFile && !util.FileExists(baseFileName+".ecx") {
+					t.Errorf("Expected .ecx to remain but it was cleaned up")
+				}
+			}
+
+			// Verify load expectations
+			if tt.expectLoadSuccess {
+				if diskLocation.EcShardCount() == 0 {
+					t.Errorf("Expected EC shards to be loaded for volume %d", tt.volumeId)
+				}
+			}
+
+		})
+	}
+}
+
+// TestValidateEcVolume tests the validateEcVolume function
+func TestValidateEcVolume(t *testing.T) {
+	tempDir := t.TempDir()
+
+	minFreeSpace := util.MinFreeSpace{Type: util.AsPercent, Percent: 1, Raw: "1"}
+	diskLocation := &DiskLocation{
+		Directory:     tempDir,
+		DirectoryUuid: "test-uuid",
+		IdxDirectory:  tempDir,
+		DiskType:      types.HddType,
+		MinFreeSpace:  minFreeSpace,
+	}
+
+	tests := []struct {
+		name          string
+		volumeId      needle.VolumeId
+		collection    string
+		createDatFile bool
+		numShards     int
+		expectValid   bool
+	}{
+		{
+			name:          "Valid: .dat exists with 10+ shards",
+			volumeId:      200,
+			collection:    "",
+			createDatFile: true,
+			numShards:     10,
+			expectValid:   true,
+		},
+		{
+			name:          "Invalid: .dat exists with < 10 shards",
+			volumeId:      201,
+			collection:    "",
+			createDatFile: true,
+			numShards:     9,
+			expectValid:   false,
+		},
+		{
+			name:          "Valid: .dat deleted (distributed EC) with any shards",
+			volumeId:      202,
+			collection:    "",
+			createDatFile: false,
+			numShards:     5,
+			expectValid:   true,
+		},
+		{
+			name:          "Valid: .dat deleted (distributed EC) with no shards",
+			volumeId:      203,
+			collection:    "",
+			createDatFile: false,
+			numShards:     0,
+			expectValid:   true,
+		},
+		{
+			name:          "Invalid: zero-byte shard files should not count",
+			volumeId:      204,
+			collection:    "",
+			createDatFile: true,
+			numShards:     0, // Will create 10 zero-byte files below
+			expectValid:   false,
+		},
+		{
+			name:          "Invalid: .dat exists with different size shards",
+			volumeId:      205,
+			collection:    "",
+			createDatFile: true,
+			numShards:     10, // Will create shards with varying sizes
+			expectValid:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			baseFileName := erasure_coding.EcShardFileName(tt.collection, tempDir, int(tt.volumeId))
+
+			// For proper testing, we need to use realistic sizes that match EC encoding
+			// EC uses large blocks (1GB) and small blocks (1MB)
+			// For test purposes, use a small .dat file size that still exercises the logic
+			// 10MB .dat file = 1MB per shard (one small batch, fast and deterministic)
+			datFileSize := int64(10 * 1024 * 1024) // 10MB
+			expectedShardSize := calculateExpectedShardSize(datFileSize)
+
+			// Create .dat file if needed
+			if tt.createDatFile {
+				datFile, err := os.Create(baseFileName + ".dat")
+				if err != nil {
+					t.Fatalf("Failed to create .dat file: %v", err)
+				}
+				// Write minimal data (don't need to fill entire 10GB for tests)
+				datFile.Truncate(datFileSize)
+				datFile.Close()
+			}
+
+			// Create EC shard files with correct size
+			for i := 0; i < tt.numShards; i++ {
+				shardFile, err := os.Create(baseFileName + erasure_coding.ToExt(i))
+				if err != nil {
+					t.Fatalf("Failed to create shard file: %v", err)
+				}
+				// Use truncate to create file of correct size without allocating all the space
+				if err := shardFile.Truncate(expectedShardSize); err != nil {
+					shardFile.Close()
+					t.Fatalf("Failed to truncate shard file: %v", err)
+				}
+				if err := shardFile.Close(); err != nil {
+					t.Fatalf("Failed to close shard file: %v", err)
+				}
+			}
+
+			// For zero-byte test case, create empty files for all data shards
+			if tt.volumeId == 204 {
+				for i := 0; i < erasure_coding.DataShardsCount; i++ {
+					shardFile, err := os.Create(baseFileName + erasure_coding.ToExt(i))
+					if err != nil {
+						t.Fatalf("Failed to create empty shard file: %v", err)
+					}
+					// Don't write anything - leave as zero-byte
+					shardFile.Close()
+				}
+			}
+
+			// For mismatched shard size test case, create shards with different sizes
+			if tt.volumeId == 205 {
+				for i := 0; i < erasure_coding.DataShardsCount; i++ {
+					shardFile, err := os.Create(baseFileName + erasure_coding.ToExt(i))
+					if err != nil {
+						t.Fatalf("Failed to create shard file: %v", err)
+					}
+					// Write different amount of data to each shard
+					data := make([]byte, 100+i*10)
+					shardFile.Write(data)
+					shardFile.Close()
+				}
+			}
+
+			// Test validation
+			isValid := diskLocation.validateEcVolume(tt.collection, tt.volumeId)
+			if isValid != tt.expectValid {
+				t.Errorf("Expected validation result %v but got %v", tt.expectValid, isValid)
+			}
+		})
+	}
+}
+
+// TestRemoveEcVolumeFiles tests the removeEcVolumeFiles function
+func TestRemoveEcVolumeFiles(t *testing.T) {
+	tests := []struct {
+		name           string
+		separateIdxDir bool
+	}{
+		{"Same directory for data and index", false},
+		{"Separate idx directory", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tempDir := t.TempDir()
+
+			var dataDir, idxDir string
+			if tt.separateIdxDir {
+				dataDir = filepath.Join(tempDir, "data")
+				idxDir = filepath.Join(tempDir, "idx")
+				os.MkdirAll(dataDir, 0755)
+				os.MkdirAll(idxDir, 0755)
+			} else {
+				dataDir = tempDir
+				idxDir = tempDir
+			}
+
+			minFreeSpace := util.MinFreeSpace{Type: util.AsPercent, Percent: 1, Raw: "1"}
+			diskLocation := &DiskLocation{
+				Directory:     dataDir,
+				DirectoryUuid: "test-uuid",
+				IdxDirectory:  idxDir,
+				DiskType:      types.HddType,
+				MinFreeSpace:  minFreeSpace,
+			}
+
+			volumeId := needle.VolumeId(300)
+			collection := ""
+			dataBaseFileName := erasure_coding.EcShardFileName(collection, dataDir, int(volumeId))
+			idxBaseFileName := erasure_coding.EcShardFileName(collection, idxDir, int(volumeId))
+
+			// Create all EC shard files in data directory
+			for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+				shardFile, err := os.Create(dataBaseFileName + erasure_coding.ToExt(i))
+				if err != nil {
+					t.Fatalf("Failed to create shard file: %v", err)
+				}
+				if _, err := shardFile.WriteString("dummy shard data"); err != nil {
+					shardFile.Close()
+					t.Fatalf("Failed to write shard file: %v", err)
+				}
+				if err := shardFile.Close(); err != nil {
+					t.Fatalf("Failed to close shard file: %v", err)
+				}
+			}
+
+			// Create .ecx file in idx directory
+			ecxFile, err := os.Create(idxBaseFileName + ".ecx")
+			if err != nil {
+				t.Fatalf("Failed to create .ecx file: %v", err)
+			}
+			if _, err := ecxFile.WriteString("dummy ecx data"); err != nil {
+				ecxFile.Close()
+				t.Fatalf("Failed to write .ecx file: %v", err)
+			}
+			if err := ecxFile.Close(); err != nil {
+				t.Fatalf("Failed to close .ecx file: %v", err)
+			}
+
+			// Create .ecj file in idx directory
+			ecjFile, err := os.Create(idxBaseFileName + ".ecj")
+			if err != nil {
+				t.Fatalf("Failed to create .ecj file: %v", err)
+			}
+			if _, err := ecjFile.WriteString("dummy ecj data"); err != nil {
+				ecjFile.Close()
+				t.Fatalf("Failed to write .ecj file: %v", err)
+			}
+			if err := ecjFile.Close(); err != nil {
+				t.Fatalf("Failed to close .ecj file: %v", err)
+			}
+
+			// Create .dat file in data directory (should NOT be removed)
+			datFile, err := os.Create(dataBaseFileName + ".dat")
+			if err != nil {
+				t.Fatalf("Failed to create .dat file: %v", err)
+			}
+			if _, err := datFile.WriteString("dummy dat data"); err != nil {
+				datFile.Close()
+				t.Fatalf("Failed to write .dat file: %v", err)
+			}
+			if err := datFile.Close(); err != nil {
+				t.Fatalf("Failed to close .dat file: %v", err)
+			}
+
+			// Call removeEcVolumeFiles
+			diskLocation.removeEcVolumeFiles(collection, volumeId)
+
+			// Verify all EC shard files are removed from data directory
+			for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+				shardFile := dataBaseFileName + erasure_coding.ToExt(i)
+				if util.FileExists(shardFile) {
+					t.Errorf("Shard file %d should be removed but still exists", i)
+				}
+			}
+
+			// Verify .ecx file is removed from idx directory
+			if util.FileExists(idxBaseFileName + ".ecx") {
+				t.Errorf(".ecx file should be removed but still exists")
+			}
+
+			// Verify .ecj file is removed from idx directory
+			if util.FileExists(idxBaseFileName + ".ecj") {
+				t.Errorf(".ecj file should be removed but still exists")
+			}
+
+			// Verify .dat file is NOT removed from data directory
+			if !util.FileExists(dataBaseFileName + ".dat") {
+				t.Errorf(".dat file should NOT be removed but was deleted")
+			}
+		})
+	}
+}
+
+// TestEcCleanupWithSeparateIdxDirectory tests EC cleanup when idx directory is different
+func TestEcCleanupWithSeparateIdxDirectory(t *testing.T) {
+	tempDir := t.TempDir()
+
+	idxDir := filepath.Join(tempDir, "idx")
+	dataDir := filepath.Join(tempDir, "data")
+	os.MkdirAll(idxDir, 0755)
+	os.MkdirAll(dataDir, 0755)
+
+	minFreeSpace := util.MinFreeSpace{Type: util.AsPercent, Percent: 1, Raw: "1"}
+	diskLocation := &DiskLocation{
+		Directory:     dataDir,
+		DirectoryUuid: "test-uuid",
+		IdxDirectory:  idxDir,
+		DiskType:      types.HddType,
+		MinFreeSpace:  minFreeSpace,
+	}
+	diskLocation.volumes = make(map[needle.VolumeId]*Volume)
+	diskLocation.ecVolumes = make(map[needle.VolumeId]*erasure_coding.EcVolume)
+
+	volumeId := needle.VolumeId(400)
+	collection := ""
+
+	// Create shards in data directory (shards only go to Directory, not IdxDirectory)
+	dataBaseFileName := erasure_coding.EcShardFileName(collection, dataDir, int(volumeId))
+	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+		shardFile, err := os.Create(dataBaseFileName + erasure_coding.ToExt(i))
+		if err != nil {
+			t.Fatalf("Failed to create shard file: %v", err)
+		}
+		if _, err := shardFile.WriteString("dummy shard data"); err != nil {
+			t.Fatalf("Failed to write shard file: %v", err)
+		}
+		if err := shardFile.Close(); err != nil {
+			t.Fatalf("Failed to close shard file: %v", err)
+		}
+	}
+
+	// Create .dat in data directory
+	datFile, err := os.Create(dataBaseFileName + ".dat")
+	if err != nil {
+		t.Fatalf("Failed to create .dat file: %v", err)
+	}
+	if _, err := datFile.WriteString("dummy data"); err != nil {
+		t.Fatalf("Failed to write .dat file: %v", err)
+	}
+	if err := datFile.Close(); err != nil {
+		t.Fatalf("Failed to close .dat file: %v", err)
+	}
+
+	// Do not create .ecx: trigger orphaned-shards cleanup when .dat exists
+
+	// Run loadAllEcShards
+	loadErr := diskLocation.loadAllEcShards()
+	if loadErr != nil {
+		t.Logf("loadAllEcShards error: %v", loadErr)
+	}
+
+	// Verify cleanup occurred in data directory (shards)
+	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+		shardFile := dataBaseFileName + erasure_coding.ToExt(i)
+		if util.FileExists(shardFile) {
+			t.Errorf("Shard file %d should be cleaned up but still exists", i)
+		}
+	}
+
+	// Verify .dat in data directory still exists (only EC files are cleaned up)
+	if !util.FileExists(dataBaseFileName + ".dat") {
+		t.Errorf(".dat file should remain but was deleted")
+	}
+}
+
+// TestDistributedEcVolumeNoFileDeletion verifies that distributed EC volumes
+// (where .dat is deleted) do NOT have their shard files deleted when load fails
+// This tests the critical bug fix where DestroyEcVolume was incorrectly deleting files
+func TestDistributedEcVolumeNoFileDeletion(t *testing.T) {
+	tempDir := t.TempDir()
+
+	minFreeSpace := util.MinFreeSpace{Type: util.AsPercent, Percent: 1, Raw: "1"}
+	diskLocation := &DiskLocation{
+		Directory:     tempDir,
+		DirectoryUuid: "test-uuid",
+		IdxDirectory:  tempDir,
+		DiskType:      types.HddType,
+		MinFreeSpace:  minFreeSpace,
+		ecVolumes:     make(map[needle.VolumeId]*erasure_coding.EcVolume),
+	}
+
+	collection := ""
+	volumeId := needle.VolumeId(500)
+	baseFileName := erasure_coding.EcShardFileName(collection, tempDir, int(volumeId))
+
+	// Create EC shards (only 5 shards - less than DataShardsCount, but OK for distributed EC)
+	numDistributedShards := 5
+	for i := 0; i < numDistributedShards; i++ {
+		shardFile, err := os.Create(baseFileName + erasure_coding.ToExt(i))
+		if err != nil {
+			t.Fatalf("Failed to create shard file: %v", err)
+		}
+		if _, err := shardFile.WriteString("dummy shard data"); err != nil {
+			shardFile.Close()
+			t.Fatalf("Failed to write shard file: %v", err)
+		}
+		if err := shardFile.Close(); err != nil {
+			t.Fatalf("Failed to close shard file: %v", err)
+		}
+	}
+
+	// Create .ecx file to trigger EC loading
+	ecxFile, err := os.Create(baseFileName + ".ecx")
+	if err != nil {
+		t.Fatalf("Failed to create .ecx file: %v", err)
+	}
+	if _, err := ecxFile.WriteString("dummy ecx data"); err != nil {
+		ecxFile.Close()
+		t.Fatalf("Failed to write .ecx file: %v", err)
+	}
+	if err := ecxFile.Close(); err != nil {
+		t.Fatalf("Failed to close .ecx file: %v", err)
+	}
+
+	// NO .dat file - this is a distributed EC volume
+
+	// Run loadAllEcShards - this should fail but NOT delete shard files
+	loadErr := diskLocation.loadAllEcShards()
+	if loadErr != nil {
+		t.Logf("loadAllEcShards returned error (expected): %v", loadErr)
+	}
+
+	// CRITICAL CHECK: Verify shard files still exist (should NOT be deleted)
+	for i := 0; i < 5; i++ {
+		shardFile := baseFileName + erasure_coding.ToExt(i)
+		if !util.FileExists(shardFile) {
+			t.Errorf("CRITICAL BUG: Shard file %s was deleted for distributed EC volume!", shardFile)
+		}
+	}
+
+	// Verify .ecx file still exists (should NOT be deleted for distributed EC)
+	if !util.FileExists(baseFileName + ".ecx") {
+		t.Errorf("CRITICAL BUG: .ecx file was deleted for distributed EC volume!")
+	}
+
+	t.Logf("SUCCESS: Distributed EC volume files preserved (not deleted)")
+}