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Volume management
37 Dell EMC SC Series: Red Hat Enterprise Linux Best Practices | CML1031
• When view volumes are first created, they consume no storage because they share the same blocks
as their parent snapshot at the beginning. As new data is written or changes are made to the existing
data, new data blocks are allocated and tracked separately from the parent. Changes made to the
view volumes do not affect the data on the parent volumes.
• Similar to regular volumes, many of the attributes, such as snapshot profiles, replications, data
reduction profile, and QoS profiles, are also available to view volumes.
• At the time the view volumes are created, the data on them are exactly the same as the parent
volumes. This includes any filesystem labels, volume partitions, UUIDs, and LVM metadata.
However, they have different SC Series volume serial IDs, LUN IDs, and WWNs.
• View volumes are read-writeable by default but can be restricted to read-only if desired.
3.12.2 Snapshot use cases
Snapshots (and view volumes) are suitable for various uses:
• Create full-size development and test environments from production
• Test new code, patches, or data changes in a production replica
• Offload backup and restore processing
• Enable fast application/data protection before major changes happen and gain the ability to quickly
roll back changes if necessary
3.12.3 Restoring data from a snapshot
Once snapshots are taken, data on these snapshots can be accessed through the view volumes. The
following subsections outline several ways to restore the data back to the Linux system.
3.12.3.1 Replace parent volumes with view volumes
In this scenario, the current data is replaced with a point-in-time copy of the data.
1. Create view volumes from the desired snapshots in the DSM GUI.
2. If applicable, stop the applications, unmount the filesystems, and export the LVM volume groups
associated with the parent volumes.
3. Remove and unmap the parent volumes from the Linux system. See section 3.10.
4. Map the view volumes to the Linux system.
5. Scan for the view volumes.
6. Since the view volumes contain the exact same metadata, including the labels, UUIDs, and LVM
names, there are no further changes needed. Simply activate the LVM volume group and mount the
filesystem.
7. Validate the restored data and start the application.
8. To roll back the process in the event of an issue, unmap the view volumes and remap the parent
volumes.
9. Do not delete the parent volumes until the restore is successfully and fully validated.
3.12.3.2 Mount view volumes on an alternate system to extract data
In this scenario, an alternate system that has a similar configuration as the parent system is used to access
the data on the view volumes.
1. Create view volumes from the desired snapshots in the DSM GUI.
2. Map the view volumes to an alternate Linux system.
3. Scan for the view volumes.
4. Import the LVM volume group and mount the filesystem.