Chapter 10. Reclaiming space on target volumes The deleted files or chunks of zero data Sometimes take up storage space on the Ceph cluster resulting in inaccurate reporting of the available storage space. The reclaim space operation removes such discrepancies by executing the following operations on the target volume: fstrim - This operation is executed on volumes that are in Filesystem mode and only if the volume is mounted to a pod at the time of execution of reclaim space operation. rbd sparsify - This operation is executed when the volume is not attached to any pods and reclaims the space occupied by chunks of 4M-sized zeroed data. Note The reclaim space operation is supported only by the Ceph RBD volumes. The reclaim space operation involves a performance penalty when it is being executed. You can use one of the following methods to reclaim the space: Enabling reclaim space operation using Annotating PersistentVolumeClaims (Recommended method to use for enabling reclaim space operation) Enabling reclaim space operation using ReclaimSpaceJob Enabling reclaim space operation using ReclaimSpaceCronJob 10.1. Enabling reclaim space operation using Annotating PersistentVolumeClaims Use this procedure to annotate PersistentVolumeClaims so that it can invoke the reclaim space operation automatically based on a given schedule. Note The schedule value is in the same format as the Kubernetes CronJobs which sets the and/or interval of the recurring operation request. Recommended schedule interval is @weekly . If the schedule interval value is empty or in an invalid format, then the default schedule value is set to @weekly . Minimum supported interval between each scheduled operation is at least 24 hours. For example, @daily (At 00:00 every day) or 0 3 * * * (At 3:00 every day). Schedule the ReclaimSpace operation during off-peak, maintenance window, or the interval when the workload input/output is expected to be low. ReclaimSpaceCronJob is recreated when the schedule is modified. It is automatically deleted when the annotation is removed. Procedure Get the persistent volume claim (PVC) details. Add annotation reclaimspace.csiaddons.openshift.io/schedule=@monthly to the PVC to create reclaimspacecronjob . Verify that reclaimspacecronjob is created in the format, "<pvc-name>-xxxxxxx" . Modify the schedule to run this job automatically. Verify that the schedule for reclaimspacecronjob has been modified. 10.2. Enabling reclaim space operation using ReclaimSpaceJob ReclaimSpaceJob is a namespaced custom resource (CR) designed to invoke reclaim space operation on the target volume. This is a one time method that immediately starts the reclaim space operation. You have to repeat the creation of ReclaimSpaceJob CR to repeat the reclaim space operation when required. Note Recommended interval between the reclaim space operations is weekly . Ensure that the minimum interval between each operation is at least 24 hours . Schedule the reclaim space operation during off-peak, maintenance window, or when the workload input/output is expected to be low. Procedure Create and apply the following custom resource for reclaim space operation: where, target Indicates the volume target on which the operation is performed. persistentVolumeClaim Name of the PersistentVolumeClaim . backOfflimit Specifies the maximum number of retries before marking the reclaim space operation as failed . The default value is 6 . The allowed maximum and minimum values are 60 and 0 respectively. retryDeadlineSeconds Specifies the duration in which the operation might retire in seconds and it is relative to the start time. The value must be a positive integer. The default value is 600 seconds and the allowed maximum value is 1800 seconds. timeout Specifies the timeout in seconds for the grpc request sent to the CSI driver. If the timeout value is not specified, it defaults to the value of global reclaimspace timeout. Minimum allowed value for timeout is 60. Delete the custom resource after completion of the operation. 10.3. Enabling reclaim space operation using ReclaimSpaceCronJob ReclaimSpaceCronJob invokes the reclaim space operation based on the given schedule such as daily, weekly, and so on. You have to create ReclaimSpaceCronJob only once for a persistent volume claim. The CSI-addons controller creates a ReclaimSpaceJob at the requested time and interval with the schedule attribute. Note Recommended schedule interval is @weekly . Minimum interval between each scheduled operation should be at least 24 hours. For example, @daily (At 00:00 every day) or "0 3 * * *" (At 3:00 every day). Schedule the ReclaimSpace operation during off-peak, maintenance window, or the interval when workload input/output is expected to be low. Procedure Create and apply the following custom resource for reclaim space operation where, concurrencyPolicy Describes the changes when a new ReclaimSpaceJob is scheduled by the ReclaimSpaceCronJob , while a ReclaimSpaceJob is still running. The default Forbid prevents starting a new job whereas Replace can be used to delete the running job potentially in a failure state and create a new one. failedJobsHistoryLimit Specifies the number of failed ReclaimSpaceJobs that are kept for troubleshooting. jobTemplate Specifies the ReclaimSpaceJob.spec structure that describes the details of the requested ReclaimSpaceJob operation. successfulJobsHistoryLimit Specifies the number of successful ReclaimSpaceJob operations. schedule Specifieds the and/or interval of the recurring operation request and it is in the same format as the Kubernetes CronJobs . Delete the ReclaimSpaceCronJob custom resource when execution of reclaim space operation is no longer needed or when the target PVC is deleted. 10.4. Customising timeouts required for Reclaim Space Operation Depending on the RBD volume size and its data pattern, Reclaim Space Operation might fail with the context deadline exceeded error. You can avoid this by increasing the timeout value. The following example shows the failed status by inspecting -o yaml of the corresponding ReclaimSpaceJob : Example You can also set custom timeouts at global level by creating the following configmap : Example Restart the csi-addons operator pod. All Reclaim Space Operations started after the above configmap creation use the customized timeout.

Commands:
oc get pvc data-pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE data-pvc Bound pvc-f37b8582-4b04-4676-88dd-e1b95c6abf74 1Gi RWO ocs-storagecluster-ceph-rbd 20h
oc annotate pvc data-pvc "reclaimspace.csiaddons.openshift.io/schedule=@monthly"
persistentvolumeclaim/data-pvc annotated
oc get reclaimspacecronjobs.csiaddons.openshift.io
NAME SCHEDULE SUSPEND ACTIVE LASTSCHEDULE AGE data-pvc-1642663516 @monthly 3s
oc annotate pvc data-pvc "reclaimspace.csiaddons.openshift.io/schedule=@weekly" --overwrite=true
persistentvolumeclaim/data-pvc annotated
oc get reclaimspacecronjobs.csiaddons.openshift.io
NAME SCHEDULE SUSPEND ACTIVE LASTSCHEDULE AGE data-pvc-1642664617 @weekly 3s
apiVersion: csiaddons.openshift.io/v1alpha1 kind: ReclaimSpaceJob metadata: name: sample-1 spec: target: persistentVolumeClaim: pvc-1 timeout: 360
apiVersion: csiaddons.openshift.io/v1alpha1 kind: ReclaimSpaceCronJob metadata: name: reclaimspacecronjob-sample spec: jobTemplate: spec: target: persistentVolumeClaim: data-pvc timeout: 360 schedule: '@weekly' concurrencyPolicy: Forbid
Status: Completion Time: 2023-03-08T18:56:18Z Conditions: Last Transition Time: 2023-03-08T18:56:18Z Message: Failed to make controller request: context deadline exceeded Observed Generation: 1 Reason: failed Status: True Type: Failed Message: Maximum retry limit reached Result: Failed Retries: 6 Start Time: 2023-03-08T18:33:55Z
apiVersion: v1 kind: ConfigMap metadata: name: csi-addons-config namespace: openshift-storage data: "reclaim-space-timeout": "6m"
delete po -n openshift-storage -l "app.kubernetes.io/name=csi-addons"