Important information for those who have already adopted vSphere 8.0 U2. This issue is not present in ANY previous vSphere versions.
There's a possibility that the CBT corruption bug from 8 years ago was reintroduced in 8.0 U2 as we're able to reproduce it reliably in our labs at least in some configurations. We have opened a support case with VMware and will do a wider customer announcement if/when they confirm the issue and its scope from their side.
If you're on vSphere 8.0 U2 and want to act immediately, you can do the following:
1. Apparently we still have an atavism implemented to fight the original issue and QA has confirmed that after long 8 years still works in V12! Create the ResetCBTOnDiskResize (DWORD, 1) registry value to prevent this issue for any NEW disk size changes from that moment on. This value goes to the usual HKLM\SOFTWARE\Veeam\Veeam Backup and Replication key on the backup server. You will want to remove it after VMware patches the issue, as this setting will increase your backup window each time a disk is resized.
2. You cannot "fix" your existing backups but you can ensure your future backups are good. For that you should reset CBT on all your vSphere VMs that have had their disk resized following the upgrade to vSphere 8.0 U2 (not before). There are a couple of approaches you can use:
a) You can use this VMware KB > https://kb.vmware.com/s/article/2139574 , or
b) You can instead perform an Active Full backup in Veeam, ensuring the Reset CBT on each Active Full backup automatically is selected (which is the default setting).
There's a possibility that the CBT corruption bug from 8 years ago was reintroduced in 8.0 U2 as we're able to reproduce it reliably in our labs at least in some configurations. We have opened a support case with VMware and will do a wider customer announcement if/when they confirm the issue and its scope from their side.
If you're on vSphere 8.0 U2 and want to act immediately, you can do the following:
1. Apparently we still have an atavism implemented to fight the original issue and QA has confirmed that after long 8 years still works in V12! Create the ResetCBTOnDiskResize (DWORD, 1) registry value to prevent this issue for any NEW disk size changes from that moment on. This value goes to the usual HKLM\SOFTWARE\Veeam\Veeam Backup and Replication key on the backup server. You will want to remove it after VMware patches the issue, as this setting will increase your backup window each time a disk is resized.
2. You cannot "fix" your existing backups but you can ensure your future backups are good. For that you should reset CBT on all your vSphere VMs that have had their disk resized following the upgrade to vSphere 8.0 U2 (not before). There are a couple of approaches you can use:
a) You can use this VMware KB > https://kb.vmware.com/s/article/2139574 , or
b) You can instead perform an Active Full backup in Veeam, ensuring the Reset CBT on each Active Full backup automatically is selected (which is the default setting).
Statistics: Posted by Gostev — Dec 09, 2023 11:09 am
