Zerto issue with VMware VSAN – Zerto-migrated VMs unable to perform snapshot or clone

I recently used Zerto migrate VMs from an old vSphere 5.0 cluster into a new VSAN 6.6 cluster.

The VMs started up fine but I found that I could not perform any disk related functions such as snapshots or clones to the migrated VMs. All VMs that were manually created on the VSAN 6.6 cluster did not have this issue.

Error when performing a snapshot:

File was not found An error occurred while taking a snapshot: The system cannot find the file specified.

An error occurred while saving the snapshot: The system cannot find the file specified.

Cloning operation fails with error “File /vmfs/volumes/vsan:528f7d2f21f7d596-19601cad650db1f6/7e7d9c5a-e463-1a32-012c-00ee12ff003f/zertotest.vmdk was not found”.

However browsing to the directory shows the following files and the vmdk file (pointer) can clearly be found.

[root@m2mgtesx01:/vmfs/volumes/vsan:528f7d2f21f7d596-19601cad650db1f6/7e7d9c5a-e463-1a32-012c-00ee12ff003f] ls -al

total 792592

drwxr-xr-t 1 root root 2940 Mar 4 23:15 .

drwxr-xr-x 1 root root 512 Mar 4 23:25 ..

rw------ 1 root root 0 Mar 4 23:15 .0a7e9c5a-31f4-3cf9-de84-00ee12ff003f.lck

rw------ 1 root root 0 Mar 4 23:13 .127d9c5a-5f69-4ede-77bd-00ee12ff003f.lck

drwxr-xr-x 1 root root 420 Mar 4 23:13 .dvsData

rw------ 1 root root 0 Mar 4 23:14 .e47d9c5a-c6ed-3f1f-d434-00ee12ff003f.lck

r------- 1 root root 1441792 Mar 4 23:13 .fbb.sf

r------- 1 root root 267026432 Mar 4 23:13 .fdc.sf

r------- 1 root root 1179648 Mar 4 23:13 .pb2.sf

r------- 1 root root 268435456 Mar 4 23:13 .pbc.sf

r------- 1 root root 262733824 Mar 4 23:13 .sbc.sf

drwx------ 1 root root 280 Mar 4 23:13 .sdd.sf

r------- 1 root root 4194304 Mar 4 23:13 .vh.sf

rw-rr- 1 root root 231402 Mar 4 23:15 vmware.log

rw------ 1 root root 298 Mar 4 23:14 zertotest-000001.vmdk

rw------ 1 root root 298 Mar 4 23:15 zertotest-000002.vmdk

rw-rr- 1 root root 296 Mar 4 23:13 zertotest-6b40fe86.hlog

rw------ 1 root root 8684 Mar 4 23:15 zertotest.nvram

rw------ 1 root root 598 Mar 4 23:13 zertotest.vmdk

rw-rr- 1 root root 43 Mar 4 23:15 zertotest.vmsd

-rwxr-xr-x 1 root root 3158 Mar 4 23:15 zertotest.vmx

After trying several times, it seems that the snapshot files *-0000x.vmdk were being created each time I tried creating a snapshot albiet the error message, and hence the  *-00001.vmdk and *-00002.vmdk snapshot files which can be seen above. However, reading the vmdk files by performing a “cat zertotest-000001.vmdk” would show that the snapshot file was not linked to the original vmdk file.

Also, deleting the Zerto-copied VM from VSAN would leave the folder and the snapshot files behind which meant that those files were inconsistent and not linked to the original VM.

After several hours with Zerto support and also several hours later with VMware support, and trying different options such as upgrading the Zerto installations on both clusters to the latest Zerto ZVM v6.0P2, we found that Zerto does not support VM storage policies as mentioned in the Zerto forums below:

vSAN policy

After reading that article I found the workaround to the issue… The VSAN 6.6 cluster has multiple custom VM storage policies as VSAN relies heavily on the use of VM storage policies to define the raid type, IO limits, etc. The default VM storage policy for the “vSAN datastore” was set to one of the custom storage policies and all Zerto-migrated VMs were associated with the custom policy which was made the default.

Changing the Zerto-migrated VM’s storage policy back to the “vSAN Default Storage Policy” fixed the issue and the snapshot and clone functions worked again. If I changed the VM storage policy back to one of the custom policies after that, all snapshot and cloning functions were STILL working.

Therefore, the temporary solution to the problem until Zerto adds VM storage policy support is to use the “vSAN Default Storage Policy” as the datastore default policy IF using Zerto to migrate VMs. Once Zerto is no longer required for migrations, the default VM policy of the datastore can be switched to a custom policy.

 

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