we are currently in the middle of enabling REFS and Per-VM backup files. For that, we have a temporary storage - sadly formatted with 4 k blocks. We have two repositories on that volume to seperate two departments. The physical proxy which is shared by both departments has 16 cores and thus can provide 16 streams.
Now we tried 2 "resource" settings on our repos which both brought us different problems:
Limiting tasks per repo to 12:
- The backups from one department cannot completely stop the backups from the other which is good because we have specific backup-windows where the backups MUST run
- Creation of synthetic fulls takes up ALL the 12 tasks. So with 4 k blocks and the slower storage "fast" clone still takes 1-2 hours. We have 13 backup jobs, 3 of them need to create synthetics every day, that means that instead of 4 hours all backups stop for the synthetic creation and wait until it is finished. The thing is "fast clone" is not really doing much storage load according to our storage system so the system could easily write backups in that time.
- Our backup copy jobs also hang behind the synthetics and since we only have full bandwith for Veeam at night (because the line is shared) this means copy jobs do not finish in time
Not limiting tasks per repo:
- Backups get finished faster even while synthetics are running because the storage load is not that big because of fast clone.
- Copy jobs finishe in time
- If the backups are not finished in time because for example retention points are beeing deleten the backups from the other department cannot start because now the proxy connections are the limit
Is there any way to limit the number of tasks "used" by fast clone with per-VM backup chains? I guess the simplest solution would again be to disable per-VM but my worries right now are that we then would have other problems.