Topology Parameters

This is the documentation for the development version of OpenEBS.

See the latest version (4.3.x) to view the latest documentation.

The topology parameters defined in storage class helps in determining the placement of volume replicas across different nodes/pools of the cluster. A brief explanation of each parameter is as follows.

note

We support only one type of topology parameter per storage class.

"nodeAffinityTopologyLabel"#

The parameter nodeAffinityTopologyLabel will allow the placement of replicas on the node that exactly matches the labels defined in the storage class. For the case shown below, the volume replicas will be provisioned on worker-node-1 and worker-node-3 only as they match the labels specified under nodeAffinityTopologyLabel in storage class which is equal to zone=us-west-1.

Command

cat <<EOF | kubectl create -f -
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: mayastor-1
parameters:
  protocol: nvmf
  repl: "2"
  nodeAffinityTopologyLabel: |
    zone: us-west-1
provisioner: io.openebs.csi-mayastor
volumeBindingMode: Immediate
EOF

Apply the labels to the nodes using the below command:

Command

kubectl mayastor label node worker-node-1 zone=us-west-1
kubectl mayastor label node worker-node-2 zone=eu-east-1
kubectl mayastor label node worker-node-3 zone=us-west-1

Command (Get nodes)

kubectl mayastor get nodes -n openebs --show-labels
ID             GRPC ENDPOINT        STATUS  LABELS
worker-node-1  65.108.91.181:10124  Online  zone=eu-west-1
worker-node-3  65.21.4.103:10124    Online  zone=eu-east-1
worker-node-3  37.27.13.10:10124    Online  zone=us-west-1

"nodeHasTopologyKey"#

The parameter nodeHasTopologyKey will allow the placement of replicas on the nodes having a label whose key matches the key specified in the storage class.

Command

cat <<EOF | kubectl create -f -
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: mayastor-1
parameters:
  protocol: nvmf
  repl: "2"
  nodeHasTopologykey: |
    rack
provisioner: io.openebs.csi-mayastor
volumeBindingMode: Immediate
EOF

Apply the labels on the node using the below command:

Command

 # kubectl mayastor label node worker-node-1 rack=1
 # kubectl mayastor label node worker-node-2 rack=2
 # kubectl mayastor label node worker-node-3 rack=2
 
 # kubectl mayastor get nodes -n openebs --show-labels
 ID             GRPC ENDPOINT        STATUS  LABELS
 worker-node-1  65.108.91.181:10124  Online  rack=1
 worker-node-3  65.21.4.103:10124    Online  rack=2
 worker-node-3  37.27.13.10:10124    Online  rack=2

In this case, the volume replicas will be provisioned on any two of the three nodes i.e.

worker-node-1 and worker-node-2 or
worker-node-1 and worker-node-3 or
worker-node-2 and worker-node-3 as the storage class has rack as the value for nodeHasTopologyKey that matches the label key of the node.

"poolAffinityTopologyLabel"#

The parameter poolAffinityTopologyLabel will allow the placement of replicas on the pool that exactly match the labels defined in the storage class.

Command

cat <<EOF | kubectl create -f -
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: mayastor-1
parameters:
  protocol: nvmf
  repl: "2"
  poolAffinityTopologyLabel: |
    zone: us-west-1
provisioner: io.openebs.csi-mayastor
volumeBindingMode: Immediate
EOF

Apply the labels to the pools using the below command:

Command

cat <<EOF | kubectl create -f -
apiVersion: "openebs.io/v1beta2"
kind: DiskPool
metadata:
  name: pool-on-node-0
  namespace: mayastor
spec:
  node: worker-node-0
  disks: ["/dev/sdb"]
  topology:
    labelled:
        zone: us-west-1
---
apiVersion: "openebs.io/v1beta2"
kind: DiskPool
metadata:
  name: pool-on-node-1
  namespace: mayastor
spec:
  node: worker-node-1
  disks: ["/dev/sdb"]
  topology:
    labelled:
        zone: us-east-1
---
apiVersion: "openebs.io/v1beta2"
kind: DiskPool
metadata:
  name: pool-on-node-2
  namespace: mayastor
spec:
  node: worker-node-2
  disks: ["/dev/sdb"]
  topology:
    labelled:
        zone: us-west-1
EOF

Command (Get filtered pools based on labels)

kubectl mayastor get pools -n openebs --selector zone=eu-west-1
ID             GRPC ENDPOINT        STATUS  LABELS
ID              DISKS                                                     MANAGED  NODE           STATUS  CAPACITY  ALLOCATED  AVAILABLE  COMMITTED
pool-on-node-0  aio:///dev/sdb?uuid=b7779970-793c-4dfa-b8d7-03d5b50a45b8  true     worker-node-0  Online  10GiB     0 B        10GiB      0 B
pool-on-node-2  aio:///dev/sdb?uuid=b7779970-793c-4dfa-b8d7-03d5b50a45b8  true     worker-node-2  Online  10GiB     0 B        10GiB      0 B

kubectl mayastor get pools -n openebs --selector zone=eu-east-1
ID             GRPC ENDPOINT        STATUS  LABELS
ID              DISKS                                                     MANAGED  NODE           STATUS  CAPACITY  ALLOCATED  AVAILABLE  COMMITTED
pool-on-node-1  aio:///dev/sdb?uuid=b7779970-793c-4dfa-b8d7-03d5b50a45b8  true     worker-node-1  Online  10GiB     0 B        10GiB      0 B

For the case shown above, the volume replicas will be provisioned on pool-on-node-0 and pool-on-node-2 only as they match the labels specified under poolAffinityTopologyLabel in the storage class that is equal to zone=us-west-1.

"poolHasTopologyKey"#

The parameter poolHasTopologyKey will allow the placement of replicas on the pool that has label keys same as the keys passed in the storage class.

Command

cat <<EOF | kubectl create -f -
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: mayastor-1
parameters:
  protocol: nvmf
  repl: "2"
  poolHasTopologykey: |
    zone
provisioner: io.openebs.csi-mayastor
volumeBindingMode: Immediate
EOF

Command (Get filtered pools based on labels)

kubectl mayastor get pools -n openebs --selector zone=eu-west-1
ID             GRPC ENDPOINT        STATUS  LABELS
ID              DISKS                                                     MANAGED  NODE           STATUS  CAPACITY  ALLOCATED  AVAILABLE  COMMITTED
pool-on-node-0  aio:///dev/sdb?uuid=b7779970-793c-4dfa-b8d7-03d5b50a45b8  true     worker-node-0  Online  10GiB     0 B        10GiB      0 B
pool-on-node-2  aio:///dev/sdb?uuid=b7779970-793c-4dfa-b8d7-03d5b50a45b8  true     worker-node-2  Online  10GiB     0 B        10GiB      0 B

kubectl mayastor get pools -n openebs --selector zone=eu-east-1
ID             GRPC ENDPOINT        STATUS  LABELS
ID              DISKS                                                     MANAGED  NODE           STATUS  CAPACITY  ALLOCATED  AVAILABLE  COMMITTED
pool-on-node-1  aio:///dev/sdb?uuid=b7779970-793c-4dfa-b8d7-03d5b50a45b8  true     worker-node-1  Online  10GiB     0 B        10GiB      0 B

In this case, the volume replicas will be provisioned on any two of the three pools i.e.

pool-on-node-1 and pool-on-node-2 or
pool-on-node-1 and pool-on-node-3 or
pool-on-node-2 and pool-on-node-3 as the storage class has zone as the value for poolHasTopologyKey that matches with the label key of the pool.

"stsAffinityGroup"#

stsAffinityGroup represents a collection of volumes that belong to instances of Kubernetes StatefulSet. When a StatefulSet is deployed, each instance within the StatefulSet creates its own individual volume, which collectively forms the stsAffinityGroup. Each volume within the stsAffinityGroup corresponds to a pod of the StatefulSet.

This feature enforces the following rules to ensure the proper placement and distribution of replicas and targets so that there is not any single point of failure affecting multiple instances of StatefulSet.

Anti-Affinity among single-replica volumes: This rule ensures that replicas of different volumes are distributed in such a way that there is no single point of failure. By avoiding the colocation of replicas from different volumes on the same node.
Anti-Affinity among multi-replica volumes:

If the affinity group volumes have multiple replicas, they already have some level of redundancy. This feature ensures that in such cases, the replicas are distributed optimally for the stsAffinityGroup volumes.

Anti-affinity among targets:

The High Availability feature ensures that there is no single point of failure for the targets. The stsAffinityGroup ensures that in such cases, the targets are distributed optimally for the stsAffinityGroup volumes.

By default, the stsAffinityGroup feature is disabled. To enable it, modify the storage class YAML by setting the parameters.stsAffinityGroup parameter to true.

"cloneFsIdAsVolumeId"#

cloneFsIdAsVolumeId is a setting for volume clones/restores with two options: true and false. By default, it is set to false.

When set to true, the created clone/restore's filesystem uuid will be set to the restore volume's uuid. This is important because some file systems, like XFS, do not allow duplicate filesystem uuid on the same machine by default.
When set to false, the created clone/restore's filesystem uuid will be the same as the original volume uuid, but it will be mounted using the nouuid flag to bypass duplicate uuid validation.

note

This option needs to be set to true when using a btrfs filesystem, if the application using the restored volume is scheduled on the same node where the original volume is mounted, concurrently.

Topology Parameters

note

"nodeAffinityTopologyLabel"#

"nodeHasTopologyKey"#

"poolAffinityTopologyLabel"#

"poolHasTopologyKey"#

"stsAffinityGroup"#

"cloneFsIdAsVolumeId"#

note

See Also#

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