Veeam + Nutanix: “Active snapshots limit reached for datastore”

Last night I ran into an interesting “quirk” using Veeam v8 to back up my virtual machines that live on a Nutanix cluster.  We’d just moved the majority of our production workload over to the new Nutanix hardware this past weekend and last night marked the first round of backups using Veeam on it.

We ended up deploying a new Veeam backup server and proxy set on the Nutanix cluster in parallel to our existing environment.  When there were multiple jobs running concurrently overnight, many of them were in a “0% completion” state, and the individual VM’s that make up the jobs had a “Resource not ready: Active snapshots limit reached for datastore” message on them.

veeam 1

I turned to the all-knowing Google and happened across a Veeam forum post that sounded very similar to the issue I was experiencing.  I decided to open up a ticket with Veeam support since the forum post in question referenced Veeam v7, and the support engineer confirmed that there was indeed a self-imposed limit of 4 active snapshots per datastore – a “protection method” of sorts to avoid filling up a datastore.  On our previous platform, the VM’s were spread across 10+ volumes and this issue was never experienced.  However, our Nutanix cluster is configured with a single storage pool and a single container with all VM’s living on it, so we hit that limit quickly with concurrent backup jobs.

The default 4 active snapshot per datastore value can be modified by creating a registry DWORD value in ‘HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam Backup and Replication\’ called MaxSnapshotsPerDatastore and use the appropriate hex or decimal value.  I started off with ’20’ but will move up or down as necessary.  We have plenty of capacity at this time and I’m not worried at all about filling up the storage container.  However, caveat emptor here because it is still a possibility.

This “issue” wasn’t anything specific to Nutanix at all, but is increasingly likely with any platform that uses a scale-out file system that can store hundreds or thousands of virtual machines on a single container.

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