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Title
Backup fails with "Error: 2800 - filter file contains the wrong number of blocks" -
Description
Backup fails with "Error: 2800 - filter file contains the wrong number of blocks". CBT is enabled for affected VM. If CBT is off, backup succeeds. -
Cause
The particular problem described here is rare. VM was created by P2V process, apparently by VMware Converter.
One of the disks, attached to VM, has odd number of sectors. Normally this is the disk mentioned in line prior the error message. For example:Backing up disk 'vix:r:vc-vs5-suplab01.prod.quest.corp:902:[SupportFB4] ag3disk/ag3disk_2.vmdk:moref=vm-164869:snapshot-166447:6' completed.
Backup failed: Error: 2800 - filter file contains the wrong number of blocks -
Resolution
Neither VC 'Edit VM Settings' no datastore viewer will show correct disk size in bytes. To verify:
- establish SSH connection to ESX console, navigate to VM directory
cd /vmfs/volumes/<datastore>/<VM_dir>
list virtual disks with size in bytes
ls -l *flat.vmdk
get disk size and divide by 512 (bytes in sector)
If result from step 3 is an odd number, it is recommended to increase disk size up to the nearest MB or, bettter, GB. This can be done in vSphere Client.
- establish SSH connection to ESX console, navigate to VM directory
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Additional Information
Also, the number of sectors can be pulled from a vmdk header. Command is: grep RW.vmdk. For example: grep RW agRita_2.vmdk RW 4097 VMFS "agRita_2-flat.vmdk" The issue was observed when backup was configured to run in HotAdd mode. Backup may succeed in VDDK Network mode with CBT still on. In this case following line for problem disk can be seen: The change block filter failed on vix:r:vc-vs5-suplab01.prod.quest.corp:902:[SupportFB4] ag3disk/agRita_2.vmdk.