backup storage snapshots exclude swapfile

[jveerd1]

We would like to know during which step in the backup from storage snapshots process the swapfile is excluded? Which Veeam component is responsible for zeroing the blocks and how does this component identify the blocks? CBT has no clue which blocks make up the swapfile.

Veeam Backup & Replication works with HP and NetApp storage products to create backups and replicas from storage snapshots in the following way. The backup/replica job:
1. Analyzes which VMs in the job have disks on supported storage.
2. Triggers a vSphere snapshot for all VMs located on the same storage volume. (As a part of a vSphere snapshot, Veeam’s application-aware processing of each VM is performed normally.)
3. Triggers a snapshot of said storage volume once all VM snapshots have been created.
4. Retrieves the CBT information for VM snapshots created on step 2.
5. Immediately triggers the removal of the vSphere snapshots on the production VMs.
6. Mounts the storage snapshot to one of the backup proxies connected into the storage fabric.
7. Reads new and changed virtual disk data blocks directly from the storage snapshot and transports them to the backup repository or replica VM.
8. Triggers the removal storage snapshot once all VMs have been backed up.

We are having an internal discussion whether moving the swapfile to an excluded virtual disk will speed up the backup process? Since Veeam is already excluding the swapfile, the only difference is the time spend reading the changed blocks where the swapfile resides. Can anyone provide a thorough answer?

[PTide]

Hi,

As it is mentioned here and here:

<...>While copying, the source-side Veeam transport service performs additional processing — it consolidates the content of virtual disks by filtering out overlapping snapshot blocks, zero data blocks and blocks of swap files.<...>

<...>During backup, Veeam Backup & Replication checks the NTFS MFT file on VMs with Microsoft Windows OS to identify blocks of the Microsoft Windows pagefile, and excludes pagefile data blocks from processing<...>

We are having an internal discussion whether moving the swapfile to an excluded virtual disk will speed up the backup process?

That depends on OS you use. If it's Windows then it will be more convenient to use exclude swap file option (you'll need VMware tools installed for that) instead of excluding the whole disk - you'll need to add that swap disk back after recovery anyway. If you use some other OS, then the way to go will be to place your swap on an excluded drive.

Thank you.

[jveerd1]

Hi Pavel,

Thanks for answering the question.

If I understand correctly the swapfile is excluded after step 6. The only difference is the time spend zeroing and filtering out the blocks that make up the swapfile. On an averaged sized VM that difference will be negligible.

Excellent point about adding disks after recovery for the swapfile. This extra step during recovery makes the whole discussion about speeding up the backup process irrelevant for us.

[PTide]

If I understand correctly the swapfile is excluded after step 6. The only difference is the time spend zeroing and filtering out the blocks that make up the swapfile. On an averaged sized VM that difference will be negligible.

Correct. Even if your MFT is considerably large that should not cause significant delays because there is no need to scan the whole MFT every time you run a backup.

Thank you.