Cluster topology awareness in OCP GCP
You can provide your cluster topology information to Portworx using Kubernetes node labels. To understand how Portworx uses these for volumes, refer to this page.
Region and Zone information
Cloud
For OpenShift clusters on GCP, the nodes in the cluster automatically have failure domain labels applied to them. These labels correspond to the cloud provider's infrastructure characteristics, such as regions and availability zones.
Portworx parses these labels to update its understanding of the cluster topology. Users don't need to perform any additional steps.
| Label Name | Purpose |
|---|---|
| topology.kubernetes.io/region | Region in which the node resides |
| topology.kubernetes.io/zone | Zone in which the node resides |
On-premises
You can label Kubernetes nodes with following labels to inform Portworx about region and zone of the nodes.
| Label Name | Purpose |
|---|---|
| px/region | Region in which the node resides |
| px/zone | Zone in which the node resides |
Rack information
To provide rack information to Portworx, you need to label Kubernetes nodes with px/rack=rack1, where px/rack is the key and rack1 is the value identifying the rack of which the node is a part of. Make sure the label is a string not starting with a special character or a number.
Example
Following example updates rack information for a node.
Run the following command to list the existing nodes and their labels.
oc get nodes --show-labels
NAME STATUS AGE VERSION LABELS
vm-1 Ready 14d v1.7.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=vm-1,node-role.kubernetes.io/master=
vm-2 Ready 14d v1.7.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=vm-2
vm-3 Ready 14d v1.7.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=vm-3
To indicate node vm-2 is placed on rack1 update the node label in the following way:
oc label nodes vm-2 px/rack=rack1
Now let's check your updated node labels.
oc get nodes --show-labels
NAME STATUS AGE VERSION LABELS
vm-1 Ready 14d v1.7.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=vm-1,node-role.kubernetes.io/master=
vm-2 Ready 14d v1.7.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=vm-2,px/rack=rack1
vm-3 Ready 14d v1.7.4 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=vm-3
This verifies that node vm-2 has the new px/rack label.
Double check if the rack information is reflected in the Portworx cluster.
pxctl cluster provision-status
NODE NODE STATUS POOL POOL STATUS ..... ZONE REGION RACK
vm-2 Online 0 Online ..... default default rack1
vm-3 Online 0 Online ..... default default default
The node vm-2 which was labelled rack1 is reflected on the Portworx node while the unlabelled node vm-3 is still using the default rack info.
All the subsequent updates to the node labels will be automatically picked up by the Portworx nodes. A deletion of a px/rack label will also be reflected.
Specifying replica placement for volumes
Once the nodes are updated with rack info you can specify how the volume data can spread across your different racks.
Following is an example of a storage class that replicates its volume data across racks rack1 and rack2
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
name: px-postgres-sc
provisioner: pxd.portworx.com
parameters:
repl: "2"
shared: "true"
racks: "rack1,rack2"
Any PVC created using the above storage class will have a replication factor of 2 and will have one copy of its data on rack1 and the other copy on rack2
To do the same for regions and zones, you can use regions and zones as parameters in the StorageClass respectively.