How to customize storage options¶

This guide describes how to configure storage classes and volume sizes for COS components, using the Juju Terraform provider.

Configure custom storage class¶

You may want to use custom storage classes like Ceph or Cinder-backed PVCs for your containers. List the available storage classes:

kubectl get sc

NAME                  PROVISIONER              RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE    
ceph-ext4             rbd.csi.ceph.com         Delete          Immediate              true                   2d22h  
ceph-xfs              rbd.csi.ceph.com         Delete          Immediate              true                   2d22h  
csi-rawfile-default   rawfile.csi.openebs.io   Delete          WaitForFirstConsumer   false                  3d1h   

For example, to have all the pods deployed with a PVC that is provisioned by ceph-xfs storage class, modify the juju_model resource in the base file with a workload-storage config:

resource "juju_model" "cos" {                             
  name   = "cos"                                          
  config = { logging-config = "<root>=WARNING; unit=DEBUG"
  
+ workload-storage = "ceph-xfs"      
  }                                
}

Configure custom storage sizes¶

Since COS components are storage intensive, it is recommended to modify the size of your PVC.

Important

If you don’t specify a size, a PVC will be created with a default size of 1G backed by the storage class you configured.

Add a storage_directive for each storage container in your terraform file. For COS Lite it may look like this:

module "cos-lite" {
  source     = "git::https://github.com/canonical/observability-stack//terraform/cos-lite?ref=main" 
  model_uuid = juju_model.cos.uuid
  risk       = "edge"

+ # Adding storage for Prometheus
+ prometheus = {
+   storage_directives = { "database" = "200G" }
+ }      

+ # Adding storage for Loki
+ loki = {
+   storage_directives = { "loki-chunks" = "400G" }
+ }     

+ # Adding storage for Alertmanager (Note the key is usually "data")
+ alertmanager = {
+   storage_directives = { "data" = "100G" }
+ }
}

This shows 3 examples setting sizes for Prometheus, Loki and Alertmanager using the syntax {storage_directives = {<storage_name> = "<size>"}}

You can find the names of relevant storage volumes in the storage reference.

External links¶

Example of using storage_directives