Volume and volume groups

The refresh operation has different meanings depending on the resource type. For volumes and their thin clones, the refresh operation replaces the contents of an object with the data of another resource within the same family. For volume groups and volume group thin clones with write-order consistency enabled, the contents for all members of the group are replaced. When write-order consistency is disabled, individual volumes within a volume group can be refreshed. After a refresh operation is started, the process quickly completes since only pointer updates for the resource are changed. The refresh operation differs from a restore operation, which returns the object to a previous point-in-time copy of itself. A storage resource family consists of the parent storage resource, which is the original resource, any thin clones, and snapshots in the tree. An example is shown in Figure 8.

Figure 8.        Storage resource family example

When using the refresh operation, obtaining a backup snapshot of the current state of the resource is highly recommended. Shut down applications using the volume, take the volume offline on the hosts, and take a backup snapshot of the current state of the resource. Not only does this guard against data corruption, but it also preserves a point-in-time copy of the dataset in case it is needed. When a refresh operation is issued from PowerStore Manager, an option to take a backup snapshot is provided. This option, which is selected by default, takes a snapshot right before the refresh operation is started.

Table 2 outlines the refresh operations that are allowed for volumes, volume groups, and thin clones. The table is organized by the object to refresh, the object to refresh from, and if the operation is allowed. Footnotes below the table provide more information about the supported operations.

Table 2.      Volume and volume group refresh operations

1 Use the restore operation to complete this operation.

2 Refreshing from a snapshot of a peer, in-family, thin clone is supported. If the snapshot is of the thin clone that is being refreshed, use the restore operation.

To refresh a volume, volume group, or a thin clone from another resource, select the resource from the volume or volume group page, click Repurpose, and click Refresh Using Related Volume. The Repurpose drop-down menu replaced the More Actions drop-down menu seen in earlier versions of PowerStoreOS. In the following example, the resources in Figure 8 were re-created to show the objects that can be used as a source of the refresh operation. Select Snap 1 Thin Clone, Repurpose, and Refresh Using Related Volume, and the screen in Figure 9 is shown.

In this window, a warning is shown to remind the user to shut down applications using the volume and take the volume offline on the hosts. These operations should be performed prior to the refresh operation to prevent data integrity issues. The user is also provided with information about the resource being refreshed, in this case Snap 1 Thin Clone, and a drop-down to select the source of the new data. The Create a backup snapshot of the volume being refreshed option is also provided. As previously stated, the option to take the snapshot is enabled by default. The user can disable it, and they can customize the name of the snapshot being taken.

Figure 9.        Refresh Using Related Volume example

Figure 10 shows the drop-down option that is expanded, and the volumes available as a source of the refresh operation for Snap 1 Thin Clone. In this resource family, Snap 1 Thin Clone can be refreshed using the data from the parent resource, Storage Resource, or another thin clone, Snap 2 Thin Clone. If Snap 1 Thin Clone was used for backups or a test or development environment, Refresh can be used to quickly update the contents of the resource to provide the latest information to the user or application.

Figure 10.    Refresh Using Related Volume—Volumes available example

After selecting the source resource for the refresh operation and clicking Refresh, a confirmation window appears. To complete the operation, click Refresh. An example of the confirmation window is shown in Figure 11.

Figure 11.    Refresh Using Related Volume example

Alternatively, to refresh a volume, volume group, or any thin clones of the resource from a supported snapshot, select the snapshot from the Snapshot page within the Protection tab, click More Actions, then Refresh Using Snapshot. A window like the one in Figure 9 appears and allows the user to select a volume, volume group, or a thin clone to refresh. When it is complete, the resource contains the data that is found within the snapshot.

File systems

A file system refresh operation deletes the current contents of a snapshot and replaces it with the current data within the parent file system or file system thin clone. As with the volume and volume group refresh operation, only pointer updates occur so the operation completes quickly. This operation allows any users or applications accessing the snapshot to quickly have access to the latest information within the production file system. Figure 12 shows an example of the supported refresh operations.

Figure 12.    File system and file system thin clones refresh operation example

When a snapshot is created, values for the Creation Time and the Expiration Time are saved and displayed for the snapshot. To know which snapshots have been refreshed, the system tracks the Last Refresh Time. By default, this property does not have a value, but it is populated once the snapshot is refreshed. The Last Refresh Time is a column that is hidden by default within the Snapshots tab under the Protection tab of a resource.

To refresh the contents of a snapshot for a file system or file system thin clone, go to the properties page of the resource within PowerStore Manager. Then, select the Protection tab, select the checkbox in front of the snapshot to refresh, click More Actions, and click Refresh Using Snapshot. A window appears that confirms the Refresh Snapshot operation. An example of this window is shown in Figure 13.

Figure 13.    Refresh Snapshot confirmation window