Too many snapshots

tjkreidl

@Pilow Right, just skip the currently planned backup if a coalesce is still in progress and check again the next scheduled backup. This could potentially be implemented in the existing backup code.

Pilow

@tjkreidl either skip or wait until possible
I'm used to veeam backup & recovery that is very resilient to these corner cases, on vmware if it understands that a Datastore has too many snapshots, or some backup ressouce is not ready yet (you can throttle number of active workers on a repository or per proxy), veeam will just wait for availability and keep going.

problem with this way of doing is it can shift in time the schedule where you expect CR or backup to be happening.

but can be a problem to skip altogether, if @mchenry need compliancy of a certain number of replicas happening

waiting vs skipping, in a perfect world the devs give us a switch to choose our destiny

ps : I know XO Backup is not to be 100% mapped on Veeam functionnalities, but some of these functionnalities would really augment the XO Backup experience. just have to take into account Xen environment (no GC in vmware infrastructure)

tjkreidl

@Pilow The other thing to to consider is being cognizant of how long your backups typically take (or even, planning a worst-case condition) and defining the backup intervals accordingly.
In other words, if you know you cannot consistently do your incremental backups in less than an hour, perform them 90 minutes or two hours between backups. It's better IMO to have a solid backup less frequently than have them fail on a regular basis.

Pilow

@tjkreidl said:

It's better IMO to have a solid backup less frequently than have them fail on a regular basis.

totally agree.

McHenry

@tjkreidl
The offsite backup runs at 8 pm and takes 6/7 hours, whereas the hourly runs from 7 am to 7 pm and only take a few minutes.

The backup job has 19 VMs, suely this is not too many.

Pilow

@McHenry 19 VMs is 19 Chains of 16 VDIs
at each hourly run, a new snapshot is created (some minutes) and the oldest one is merged/garbage collected in the first snap (time undetermined)

I guess 19 merge + chain garbage collected seems to not be able to be done in the one hour timeframe before next CR is done

you possibly have a chain growing

can you check in DASHBOARD/HEALTH the unhealthy VDI section at 11 am ?

tjkreidl

@Pilow Agree.... have to be sure that garbage collection is completed or it'll never catch up if backups continue to be run without the coalesce completing.

McHenry

@tjkreidl

If each CR backup is now created as a snapshot, instead of a new VM, and the alert triggers after a VM has more than three snapshots, this logically means that the alert will trigger if the CR has a retention value greater than 3.

Have I misunderstood how the CR backup process works?

Pilow

@McHenry I dont think more than 3 snapshots triggers an error, just tested on one VM

it is not recommended for "in production" VMs, but for a CR destination, it's OK (as you would need to start a copy anyway)

your problem, failing CR jobs is probably due to garbage collection not finishing in the one hour timeframe when chain is long.

McHenry

@Pilow

CR jobs are not failing just XO reports too many snapshots under:
Dashboard >> Health

All good if I can just ignore this warning but thought best to check in case it was an issue.

I got the value of 3 from here.
https://docs.xen-orchestra.com/manage_infrastructure#too-many-snapshots

Pilow

@McHenry could you screen the health page ?
where we could see the chain length

henri9813

Hello,

I see also this behavior which is "new" since few weeks.

Previously, when a backup start:

it stake a snapshot ( if there another one before, it delete it ).
it upload the snapshot as a backup
it coalesce the backup on the remote.
end of the game.

Now, the old snapshots are not deleted anymore which can lead easily to some disk full.

Even with a retention of 1, the problem is present.

I observe this only in Backup job, not DR/CR job.

I just updated my XO to latest version, i will see if the issue is fixed.