Solution to Improve Veeam Backup and Restore Times
If your Veeam backups take a long time to complete or if they fail entirely; VMs freeze during backups; you see disk consolidation errors in vcenter; or if you simply want to speed up your backups, then our VirtuCache software is relevant.
VirtuCache Configuration to Speed Up Backup Times in Veeam
Standard Backup Process in Veeam
Symptoms of Slow Storage During Veeam Backups
How VirtuCache Changes the VM Backup Process in Veeam?
How VirtuCache Changes the VM Restore Process in Veeam?
VirtuCache is software installed in ESXi that automatically caches all storage IO from any SAN storage array to VMware host RAM or SSD. By doing so it improves the storage performance of the VMware host and all the VMs residing on the host. Within this broader scope of VirtuCache’s ability to improve storage performance is a specific feature that improves the backup performance of Veeam.
You’d install VirtuCache in the ESXi host and apply one of it’s three caching policies to VMs or Datastores – ‘Write Back with one Replica’ policy to cache all VM reads and writes, ‘Write-Through’ policy to cache only VM reads, and ‘Backup-VM’ policy to improve the performance of backups. ‘Write Back with One Replica’ and ‘Write-Through’ policies are applied to your production VMs / Datastores whose performance you want to improve. ‘Backup-VM’ is a VirtuCache policy to be applied ONLY to your Backup proxy VM(s) and it reduces the time the Veeam Proxy VM takes to backup VMs.
To explain, how VirtuCache’s ‘Backup-VM’ policy improves backup times, I will quickly explain how Veeam backup process works and how VirtuCache inserts itself in this process to speed it up.
When the Veeam backup job starts, Veeam instructs vCenter to take a snapshot of the VM it will be backing up. Veeam then attaches this snapshot to the Veeam backup proxy VM (a process called snapshot ‘Hot Add’). Here I am assuming you are using VMware snapshots with Veeam (not Storage Controller snapshots) and your Veeam proxy is a VM (not a physical server). Subsequently, Veeam’s software running in the proxy VM, ships this snapshot to your backup storage target. Once the snapshot is successfully transferred to the storage backup target, the backup is considered complete, and Veeam instructs vCenter to delete the snapshot off of the VM that was just backed up. This process then repeats itself for every VM that is being backed up by Veeam.
Here are a few symptoms that point to a storage bottleneck which in turn means that these problems can be fixed by VirtuCache, hence I am listing these symptoms here – Veeam snapshots might take a long time to get created or deleted, or the snapshots might not get deleted at all, in which case you will see ‘disk consolidation’ errors in vCenter for those VMs. Or your VMs might freeze during backups, this is because ESXi needs to ‘stun’ a VM to take its snapshot, especially if the VM has a large vdisk, the VM might freeze for a long time negatively affecting end user experience. If the storage congestion either on the production or backup target storage array / network is really bad, then backups might fail.
When VirtuCache is installed in the ESXi hosts and it is configured to cache to host RAM or SSD (host based cache media), and the VirtuCache ‘Backup-VM’ policy is applied to Veeam backup proxy VM(s), then the standard process in Veeam is modified this way – instead of vCenter creating the snapshot (that Veeam will ultimately backup) in the same Datastore as the VM, which is the standard location for the snapshot, the snapshot is instead created in the host based cache media. Thus, the snapshot creation process is extremely quick since it bypasses the storage network and storage appliance entirely and creates it directly on host RAM or NVME SSD. Similarly, after Veeam saves the snapshot to the backup storage target, it instructs vCenter to delete the snapshot from the VM, this process too happens in the host based cache media (since the snapshot now resides there), hence the snapshot deletion process happens quickly as well.1
When a VM is restored from its backup, and if the Datastore (where the VM is being restored to) has the VirtuCache ‘Write-Back One Replica’ policy, then VirtuCache will cache all writes to host based cache media meaning that all writes in VMware, including from Veeam will be first written to the host based cache media (RAM or SSD), without being written to the SAN. Essentially the entire VM will be restored to host based cache media first and hence the restore process is much quicker. Now over the span of a few minutes, VirtuCache will also flush the writes in host based cache media to backend SAN, so the restored VM does makes its way to the backend SAN that has the Datastore, but because the VM is first restored to host based cache media, the restore is extremely fast.
1 – Veeam backup process will only be accelerated by VirtuCache if Veeam backup proxy is a VM that is on an ESXi host where VirtuCache is installed, and you are using VMware snapshots (not storage controller snapshots) with Veeam. Veeam calls this configuration ‘Virtual Appliance Transport Mode’
