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@@ -141,6 +141,66 @@ spec: storage: 1Gi ``` +<br> + +# DataLocality + +DataLocality (inspired by [Longhorn](https://longhorn.io/docs/latest/high-availability/data-locality/)) allows instructing the storage-driver which volume-locations will be used or preferred in Pods to read & write. + +It auto-sets mount-options based on the location a pod is scheduled in and the locality-option wanted. +The option can be set and overridden in *Driver*, *StorageClass* and *PersistentVolume*. + +<br> + +## Setup + +Change the type of locality + +Level | Location +------------------- | -------- +Driver | Helm: `values.yaml` -> `dataLocality` <br> Or `DaemonSet` -> Container `csi-seaweedfs-plugin` -> args `--dataLocality=` +StorageClass | `parameter.dataLocality` +PersistentVolume | `spec.csi.volumeAttributes.dataLocality` + +Driver < StorageClass < PersistentVolume + +<br> + +## Available options + +Option | Effect +----------------------- | ------ +`none`* | Changes nothing +`write_preferLocalDc` | Sets the `DataCenter`-mount-option to the current Node-DataCenter, making writes local and allowing reads to occur wherever read data is stored. [More Details](#`write_preferLocalDc`) + +\* Default + +<br> + +## Requirements + +Volume-Servers and the CSI-Driver-Node need to have the locality-option `DataCenter` correctly set (currently only this option is required). + +This can be done manually (although quite tedious) or injected by the Container-Orchestration. + +<br> + +### Automatic injection + +**Kubernetes** + +Unfortunately Kubernetes doesnt allow grabbing node-labels, which contain well-known region-labels, and setting them as environment-variables. +The DownwardAPI is very limited in that regard. (see [#40610](https://github.com/kubernetes/kubernetes/issues/40610)) + +Therefore a workaround must be used. [KubeMod](https://github.com/kubemod/kubemod) can be used based on [this comment](https://github.com/kubernetes/kubernetes/issues/40610#issuecomment-1364368282). This of course requires KubeMod to be installed. + +You can activate it in the Helm-Chart `values.yaml` -> `node.injectTopologyInfoFromNodeLabel.enabled`. +`node.injectTopologyInfoFromNodeLabel.labels` decides which labels are grabbed from the node. + +It is recommended to use [well-known labels](https://kubernetes.io/docs/reference/labels-annotations-taints/#topologykubernetesioregion) to avoid confusion. + +<br> + # License [Apache v2 license](https://www.apache.org/licenses/LICENSE-2.0) |