Recovering a Corrupted SQL Volume: Snapshot or Replica
A 4 TB Microsoft SQL Server data volume named SQL-DATA on a PowerStore 3200T is protected by a protection policy that takes a snapshot every 30 minutes and retains snapshots for 8 hours. The same policy replicates the volume asynchronously to a PowerStore 1200T at a DR site every 4 hours, so the current RPO is 4 hours. At 10:05 on a Monday, an application upgrade corrupts the database. The last known good application-consistent backup is from 08:00. PowerStore snapshots exist at 09:30, 10:00, and 10:30. The DR copy is from 08:00. The business requires an RTO of less than 1 hour and wants the smallest possible data loss. The production array is healthy and has sufficient capacity for a clone.
1. Which recovery point should be used, and why? Compare the 10:00 snapshot, the 08:00 backup, and the DR copy.
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Use the 10:00 snapshot if the corruption occurred at 10:05 and the snapshot is usable. That limits data loss to about 5 minutes, keeps recovery local, and fits the sub-1-hour RTO because a clone or restore on the production array is much faster than a DR failover. The 09:30 snapshot is older and would lose 35 minutes; the 10:30 snapshot was taken after the corruption and is not a valid recovery point.
The 08:00 backup loses two hours of data and may require a full restore, which threatens the RTO. The DR copy is also from 08:00 and would require failing over to the remote array, adding operational steps and validation time. The snapshot is the best balance of low data loss and fast recovery, but it must be validated before it replaces production.
2. Outline the restore and validation steps that meet the RTO.
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First, confirm that the 10:00 snapshot is the correct point in time and that it contains a usable SQL database. Clone the snapshot to a new volume rather than overwriting SQL-DATA immediately. Map the clone to a test or staging host, attach it to a SQL instance, and run consistency checks and application validation. This keeps the corrupted production volume available for investigation and avoids a failed in-place restore.
After validation, stop the SQL service or put the database in the required state, swap the validated clone into production, and bring SQL online. Verify application connectivity, transaction logs, and backup jobs. Because the clone is local and the array is healthy, this sequence should fit within the one-hour RTO. If the clone is not valid, fall back to the 08:00 backup with a documented data-loss decision.
3. What policy changes would reduce future risk without overwhelming the array?
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Increase replication frequency from 4 hours to 1 hour or 30 minutes if WAN bandwidth and DR array capacity allow, because that directly reduces the RPO. Keep the 30-minute snapshot schedule but align retention with the actual recovery needs and test restores regularly. For SQL, ensure snapshots are application-consistent by using pre/post scripts or an integration that quiesces the database; a crash-consistent snapshot may not be reliable enough for production recovery.
Also review whether the snapshot policy and replication policy should be separated: frequent local snapshots for fast rollback, and a replication schedule sized to the DR link. Test a clone-and-validate recovery quarterly so the team knows the real RTO, not just the configured RPO.