VMware with vFRC (vSphere Flash Read Cache) Case # 01763883

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VMware with vFRC (vSphere Flash Read Cache) Case # 01763883

Veeam Logoby guru81 » Mon Apr 18, 2016 11:02 pm

I'm looking for information and advice regarding usage of Veeam with VMware and a mixed environment of some hosts using vFRC(vSphere Flash Read Cache) and some not. According to documentation from vmware backups performed using vmware snapshots on VMs utilizing vFRC can only be restored to hosts that also have vFRC. In my environment we have production hosts licensed for vFRC and do NOT have it at our offsite recovery locations which leads to this issue. The issue supposedly occurs because the snapshot also snapshot the read cache and references it(even though the read cache is redundant and if in the case of disk failure is not needed, the purpose seems to just be for migrating cache settings and not losing them if you move VMs around, which makes sense), however if you restore to a host without the cache location the VM will fail to start because it cannot locate the referenced cache location.

In a quick and dirty test i was able to confirm that it does indeed fail to start if restored to a host without vFRC:
---------
Failed to lock the file
Cannot open the disk '/vmfs/volumes/<path to vmdk>-000001.vmdk' or one of the snapshot disks it depends on.
----------

What is interesting about this test restore is that it restores as if its running on a snapshot with the disks(including disks not using vFRC) all having additional XX-000001.vmdk extensions even though it is not showing an actual snapshot, neither is the backed up VM running on a snapshot. If I restore to original location it also does not act as if its running on a snapshot or create these files, only if i restore to a non vFRC host.

If I run a disk consolidation, the "snapshot" vmdk's disappear and I can now power on the VM. But does anyone know what impact this situation is having on the state of the VM and the consistency of the backups? I'm assuming these -000001.vmdk files must be related to a redirect to the cache location, even though they don't exist on the running VM. Especially with regards to the fact I am backing up SQL servers with application aware backups, I want to make sure I understand what is going on and if running disk consolidation is a valid work around for this problem. In relation to this would it also be possible to somehow automate/script the consolidation in certain restore scenarios?

Thanks for any input.
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Re: VMware with vFRC (vSphere Flash Read Cache) Case # 01763

Veeam Logoby anglerzac » Tue Jun 07, 2016 9:14 pm

did you get any response to this?
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Re: VMware with vFRC (vSphere Flash Read Cache) Case # 01763

Veeam Logoby foggy » Thu Jun 09, 2016 12:48 pm 1 person likes this post

Ryan's case was closed due to no response from his side, but overall support engineer was able to confirm Ryan's findings:

From the information we have currently available, it would appear that the use of vFRC would carry the limitation that the VMs would only be able to be restored or replicated to another host that also has vFRC enabled, without applying a workaround to manually remove the snapshot.

As long as you don't use the box to automatically power the VM on manually and remove the snapshot first, you should be able to restore from that backup to a different host. When restoring to the same host, full VM restore should work, but I would recommend running a test of Instant Recovery (choose new location or different settings and select the same host) to verify whether that restore type encounters any issues with that configuration.
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Re: VMware with vFRC (vSphere Flash Read Cache) Case # 01763

Veeam Logoby anglerzac » Fri Jun 10, 2016 11:54 am

Our DR site hosts don't have the SSD cache I imagine a lot of people would be in the same boat, is this something Veeam will look to improve in future, like automatically consolidating these snapshots on restore before power on?
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Re: VMware with vFRC (vSphere Flash Read Cache) Case # 01763

Veeam Logoby foggy » Fri Jun 10, 2016 2:19 pm

Let's take it as a feature request.
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Re: VMware with vFRC (vSphere Flash Read Cache) Case # 01763

Veeam Logoby ngreen » Fri Jun 16, 2017 2:10 pm

I still can't see any official documentation on working with vFRC so could you please clarify the exact recovery process?

If I have backups of VMs configured to use vFRC and want to restore to different hosts that do not have vFRC, I understand this is what you already recommended as a workaround:
- The VM will restore but will not power on, so we shouldn't use the option to automatically power on the VM after restore - I'm assuming just because it will fail rather than because it will cause any corruption?
- The next step is to choose snapshots > consolidate in the vsphere client (not delete all because the snapshots caused by the flash cache will not be listed)?
- Power on the VM

Are there any other steps? Do we need to edit the configuration of the VM to remove the flash cache configuration from each VMDK before power on? Does the same issue occur if the VM configured for vFRC is backed up while powered off?

Has there been any progress in improving the way Veeam handles this, e.g. the option to automatically consolidate, or to remove the cache snapshot during backup?
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Re: VMware with vFRC (vSphere Flash Read Cache) Case # 01763

Veeam Logoby anglerzac » Tue Aug 15, 2017 8:47 am

Did you ever get a response to your recovery process with vFRC?
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