Today, VMware has published the long-awaited patch for the ESXi 6.0 CBT bug. This patch is the result of a problem, which is described in KB2114076 (Backing up a virtual machine with Change Block Tracking (CBT) enabled fails after upgrading to or installing VMware ESXi 6.0). All customers that upgraded to ESXi 6.0 or installed ESXi 6.0 were affected.
Symptoms of this bug were:
- Powering on virtual machines fails
- Expanding the size of a virtual disk fails
- Taking virtual machine quiesced snapshots fails
- Error messages like “An error occurred while taking a snapshot: msg.snapshot.error-QUIESCINGERROR” (vSphere Client), “WARNING: CBT: 191: No memory available! Called from 0x4180219af50e” (vmkernel.log) or “Creating cbt node 92b78c-cbt failed with error Cannot allocate memory (0xbad0014, Out of memory)” in the vmware.log of the affected virtual machine
A workaround was to disable CBT, which resulted in longer running backups.
You can download the patch (ESXi600-201505401-BG) from VMware to manually update your ESXi hosts. Otherwise you can use VMware Update Manager to patch your hosts. A reboot is necessary!
If you decide to manually update your hosts with this patch, you have to use the “esxcli software vib” command to install the patch.
- Download the ZIP file and upload it to a datastore that is reachable for the host you want to patch (e.g. a local datastore)
- Bring the host into the maintenance mode
- Connect with SSH to your ESXi host and run:
esxcli software vib install -d "/vmfs/volumes/datastore1/patch-directory/ESXi600-201505001.zip"
- Reboot the host and leave the maintenance mode
If you have disabled CBT for all or some of your VMs, make sure that you re-enable CBT.