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Dell Solutions Enabler 10.0.0 TimeFinder SnapVX CLI User Guide

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Snapshot policy

Snapshot policies enable users to request a stream of consistent snapshots be automatically taken on the local array for applications based on a set of attributes and schedules. These multiple, frequent, consistent point-in-time copies of data or snapshots protect your production data and allow you to recover from data corruption or other damage with minimal data loss.

NOTE:Snapshot policies are only supported on arrays running PowerMaxOS 5978.669.669 or higher.

Snapshot policies can be linked, relinked, restored, terminated similarly to manual snapshots by specifying the service level name as snapshot name and snapsetID as absolute generation number to uniquely identify the snapshot and/or snapset. A snapset refers to a set of consistent snapshots that are taken together. If for example, an SG contains 10 devices and a snapshot is taken the result is a snapset with 10 consistent snapshots.

These automated snapshots are taken by the Services Daemon (storsrvcsd) based on the specified attributes and schedule. For these details, refer to the Solutions Enabler Array Controls and Management CLI User Guide.

Rules

The following rules and restrictions apply to snapshot policies and their automated snapshots:

For Snapshot policies:
  • Snapshot policies do not support taking crash consistent snapshots across multiple arrays. Only single array crash consistency is supported.
  • A maximum of 4 policies can be assigned to an SG.
  • 20 Snapshot policies are supported per array.
  • For cascaded SGs, snapshot policies can be assigned to both the parent and child SG. If the same snapshot policy is assigned to both parent and child, the setting on the child is ignored. If a snapshot policy is assigned to the parent SG, it applies across all its child SGs.
  • Automated snapshots taken across these children are consistent. This means that a child SG can fall under as many as 8 policies: 4 from its parent and 4 from itself. If a snapshot policy is assigned to only the child SG, that policy applies to only that child. If the same snapshot policy is assigned to two child SGs, but not their parent SG, snapshots are generated independently for each of the child SGs.
  • Snapshot policies can be suspended. Suspending a policy prevents new snapshots from being taken and prevents existing snapshots from being terminated. Suspending snapshot policies can be performed either at the policy level (applying to all SGs that it is associated with) or at individual SGs that the snapshot policy has been associated with (applying only to that SG).
  • Snapshot policies can be modified except for the following actions:
    • The secure snapshot attribute on a snapshot policy cannot be modified.
    • If a snapshot policy with the secure attribute is currently associated with SGs, its Interval and Maximum Count attributes can be modified so long as their expected lifetime (TTL is the product of Interval times the Maximum count) does not decrease.
  • A snapshot policy can be deleted if it is not currently assigned to any SGs.
  • If a device no longer falls under a snapshot policy, the corresponding snapshots are put into a Pending Terminate state. They are automatically terminated once their TTL, assigned at the time they were originally taken, expires. The TTL of the automated snapshots when the snapshot policy is set up must be less than or equal to 400 Days.
  • If a snapshot policy is deleted, any snapshots that were taken against it are put into an Orphaned state, and given the _Orphaned name.
For Snapshot policy automated snapshots:
  • A maximum of 1024 snapshots can be supported on a device if there are no other snapshots present. If legacy TimeFinder sessions (symclone, vpsnap, symmir) or manual snapshots are on the device, then the number of automated snapshots on a device equals 1024 minus the manual and legacy sessions.
  • Automated snapshots are supported on both FBA and CKD devices.
  • TTL cannot be set on individual automated snapshots. TTL is assigned upon taking the snapshot.
  • Although renaming automated snapshots to another automated snapshot name is not allowed, the policy they were generated from can be renamed. In this case, all its snapshots will automatically have the new name.
  • Automated snapshots cannot be converted to a secure level snapshot. Secure snapshots can be created using secure snapshot policies only.
  • Automated snapshots can be set persistent but these snapshots can still be manually terminated by a user. Secure snapshots on the other hand can only be terminated after its secure expiration time has expired.
  • SnapVX control actions (except for bulk terminate) are not allowed on a mixture of manual and automated snapshots on devices in one single request.
  • Control actions are not allowed using relative generation numbers with the automated snapshots on the devices if the request contains snapshots with different snapsetIDs.
  • It is recommended to exercise caution when using both zDP and Solution Enabler to create snapshots on a device. Having zDP and automated or manual snapshots on a device count towards the total number of sessions. As a result, this might limit the number of the maximum count of the supported snapshot type.
  • The expiration timestamp is displayed only for automated snapshots with the Pending Delete attribute.
  • EXPIRED is displayed for secure snapshots or automated snapshots with Pending Delete state when the TTL expires.
  • Orphaned snapshots cannot be renamed, but they can still be used for link and restore operations.

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