PowerProtect: Some VMs with Transparent Snapshot Taking Over 24 hours to Replicate

• Replication of TSDM VM copies is slow from PowerProtect DD to PowerProtect DD
• Use case: VMs contain databases like SQL and the disk affected is the SQL database/log disk
• Replication of a VADP backup for the same VM completes in an expected time frame
• Some VMs running SQL and backed up with PowerProtect Data Manager TSDM showed replication times of 38 hours. Similar sized disks completed replication in 10 hours. This was due to the nature of the disk having small scattered changes.

PowerProtect DD parameter SREPL_RECIPE_MIN_LEN. 

• This key is checked during backup to decide what synthetic instructions to save for replication processing. It is also used during synthetic replication to decide what synthetic recipe instructions to replay. If this is set after the backup is complete, the replication will see the smaller synthetic instructions and simply disregard them and use the normal replication filtering protocol for these. If the backup was done after the size was increased, these smaller synthetic instructions will not even be saved to be replayed during replication.
• The key does not impact the VM workload itself. The key simply changes how the PowerProtect DD replication code processes this data. Rather than issue requests to synthesize small regions the replication process uses the normal filtering protocol to transfer these regions.
• An internal task has been created to improve replication for TSDM backups with PowerProtect Data Manager and PowerProtect DD. This may be addressed in a future release 

Fix: Not available | Expected in future DDOS release

Workaround:

• Contact Dell Technical support and reference this KB article (#000219531) to expedite resolution.
  • Support will set the relevant parameter (SREPL_RECIPE_MIN_LEN=253952) and restart the filesystem to apply the change.
    • This workaround is persistent across reboots but not DDOS upgrade.