Release Notes

20 Dell PS Series Snapshots and Clones: Best Practices and Sizing Guidelines | BP1027
A thin clone volume that was created from a template volume is dependent on the associated template
volume. Deleting a thin clone does not delete the template volume it is associated with. Before deleting a
template volume, all thin clones that depend on it must first be deleted or converted to regular volumes. If an
administrator wants to preserve one of the thin clones, a full clone volume (essentially a copy) can be created
from that thin clone before it is deleted.
4.4 Reducing backup time with snapshots and clones
Snapshots can greatly simplify and increase the performance of backup and recovery operations by providing
the ability to offload the backup copy operation to a different server than where an application is running. In
addition, they offer improvements to backup operations with regard to open file handling.
While snapshots provide a fast and efficient manner to create copies of SAN volumes, the snapshots are still
stored with the SAN volumes and may share data with the base volume. This means that both primary
application data and its snapshots are vulnerable to catastrophic loss scenarios such as fire, flood, and
earthquake. Administrative mistakes, such as deleting the volume, open the possibility to lose primary data
and associated snapshots. Therefore, snapshots should not be considered a substitute for traditional backup
technologies, but a supplement to them.
Snapshots are inherently temporary. An administrator can configure the system to keep many snapshots for
days or weeks, rather than months or years, as is typical of backup archives. Clone volumes contain a full
copy of the base volume, and can even be moved to a separate storage pool. This means they are not
dependent on the base volume, however, if they are stored in the same SAN will be vulnerable to the same
catastrophic site disasters. Using snapshots and clone volumes in conjunction with PS Series Auto-
Replication is an efficient way of creating offsite copies of volumes that can be used in the case of a disaster
at the primary site.
Well-designed backup environments ensure copies of data are regularly created and stored away from the
primary volume data. This backup data is typically stored in a secure location, and kept for months to years
depending on the retention policies of the organization. Using a combination of PS Series snapshots, clone
volumes, auto-replication, and external backups (to tape or other disk), backup data can be used both for
small data recovery operations (such as a user accidentally deleting a file) and full recovery from a
catastrophic failure in the data center.
Note: Dell strongly recommends customers run a comprehensive backup environment, and consider utilizing
snapshots or clone volumes as part of this environment to improve backup and restore operations.