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Veeam replication  is taking forever to complete.

Posted on 2012-08-30
Medium Priority
Last Modified: 2012-09-05
Hello Experts,

see http://www.experts-exchange.com/Software/VMWare/Q_27842307.html first.

I am trying out Veeam backup and replication, the replication part.

After the initial replication what took 4 days over wan i started the next incremental
replication cycle, this froze with a error.

Cannot use CBT: Soap fault. A specified parameter was not correct. on server on datastore etc

I followed instructions from http://www.veeam.com/KB1113

But it did not solve the problem, it still freezes, while the amount of data compared to
the initial replication cycle is very small.

Any ideas?
Question by:bastouw
  • 4
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LVL 125

Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 2000 total points
ID: 38349440
I would remove all the snapshots, CBT tracking files and start the process again.

Author Comment

ID: 38349690
i followed the veeam article to the letter

Would you like me to do extra things?
LVL 125
ID: 38349709
Get the fault escalated to Veeam Support.
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Author Comment

ID: 38357544
I disable ctk on the multiple times now
but it seen to auto enable, why does set cbt to true when i set it to false?
LVL 125
ID: 38357553
change block tracking is required for backups.

Author Comment

ID: 38369448
ok, how does cbt exactly work, does it take some time to catch up with the actual changed
blocks on the vmdk's?
LVL 125
ID: 38369580
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.

Author Comment

ID: 38369613
ok, clear. i have no problem anymore so i close the question.

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