Veeam: Backup jobs break after vCenter upgrade

Posted on 2013-10-01
Medium Priority
Last Modified: 2013-10-02
Has anyone heard of Veeam backup jobs breaking after doing a vCenter upgrade? If not breaking, then forcing FULL backups even though it should have done an incremental?
Question by:pzozulka
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Assisted Solution

by:Nick Rhode
Nick Rhode earned 400 total points
ID: 39538140
This happened to me and I had to remove VCenter from veeam and re-add it.  Also do this to the backup jobs as well. Remove it from the backup job, save, then re-add it to the backup job.

Author Comment

ID: 39538167
We actually haven't upgraded yet as we just heard about this being a possible issue.

Is there any way to avoid this issue within Veeam? Is there a Veeam KB article about this or a bug report?
LVL 22

Expert Comment

by:Nick Rhode
ID: 39538506
What versions are you upgrading from and to?

Author Comment

ID: 39538511
Running Veeam B&R 6.5. Upgrading vCenter 5.0 to 5.1.
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Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 1600 total points
ID: 39538981
It's possible the CTK files have been reset.

from Anton Gostev from Veeam on CBT:

In essence, CBT is all about CTK files, these are the files which contain change tracking information of the corresponding VMDK file.

The concept is pretty simple, and if you are familiar with AD DirSync control, or Exchange ICS (public folders change tracking) – it is essentially the same: global USN (Update Sequence Number) for each object. CTK file describes the state of each block for tracking purposes, and contain USN for each block in the corresponding VMDK. After any block is updated, it is assigned the new global USN (which is previous USN value that was used on previously processed block plus 1). This way, any application can ask VMware API “tell me if this block was changed since THIS moment”, and the API will easily tell that by simply comparing the provided sequence number with the actual USN on each block. If provided USN is smaller than actual for particular block, it means that the block was changed (and needs to be backed up, replicated or otherwise processed). So multiple processes cannot conflict with each other anyhow. Each process just memorizes the USN corresponding to the snapshot that the application created during processing, and next time it will use the memorized USN to query for changed blocks.

There should be one CTK file per VMDK file, and CTK file cannot grow out of proportion with number of blocks in VMDK (as it stores only 1 record per VMDK block). CTK file is also thousands time smaller than actual VMDK, because it stores only a few bytes of information (USN) for each corresponding 256KB VMDK block (I am 90% sure it is 256KB, used to calculate it once using CTK debug/stats data, just don’t remember for sure – unimportant info escapes my head automatically to prevent overload with useless facts ;) . For the same reasons, I/O overhead is barely noticeable with CBT: change few extra bytes to write for each 256000 bytes of data.

The CTK files are permanent, and should not be deleted after backup/replication.

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