Change Block Tracking mode limitation with snapshot

[damduq]

Hello

I've just installed Veeam backup 4 for testing.
First backup was slow (network mode is at the moment the only possible, I haven't yet received my SANs...)
But unfortunately, next backups were also slow, due to impossibility to activate Changed Block Tracking mode.
It says that it's not possible to use this mode with snapshots on the VM.

Is it because of VMware limitation ?

If I use the internal SANs snapshots, will it be possible to activate Changed Block Tracking ?

One of my VM was CBT compliant, and then it's increadibly faster !!!

Thank's for your ideas.

[Gostev]

Yes, changed block tracking cannot be enabled if VM has snapshots - it is VMware limitation. Remove all snapshots, let Veeam Backup enable change block tracking on a VM, then you can create snapshots again. Snapshots do not prevent changed block tracking from functioning once it is enabled.

[damduq]

Excellent.

Thank's

[damduq]

And good job from Veeam Team. I'm impressed.

[ivanildogalvao]

Friends, one of our customer has the Veeam 6 installed, runs nightly backup of virtual machines, the job contains six VMS, one with 180GB is presenting the following warning "Warning 23:01:09 00:06:27 + a 140.0 GB 138.0 GB 1.5 GB 1:05:17 Changed block tracking can not be enabled: one or more snapshots present "

Why does this happen? Should I be concerned?

Thank you!

[dellock6]

CBT must be enabled at first time with no snapshots on the VM. Try to remove the snapshot first and than try again.
If it does not work, you have to reset CBT, there are some threads in this forum about how to do that.

[0zzY]

Hi all,
i have configured a backup job with mixed os virtual machine (some linux and windows) using veeam B&R 6.1 and vmware single host v 5.0.0 build 623860

I get this error "Changed block tracking cannot be enabled: one or more snapshots present" after backup of the File Server machine (win 2008).
In the vsphere client snapshoot manager i have seen that there is a temporary snapshoot taken.

How can i fix it?

[0zzY]

CBT must be enabled at first time with no snapshots on the VM. Try to remove the snapshot first and than try again.
If it does not work, you have to reset CBT, there are some threads in this forum about how to do that.

So have i to do remove the snapshoot created by veeam and then run the backup job again?

[foggy]

Yes, you can delete this snapshot via vSphere Client manually.

[Vitaliy S.]

Yes, if you do not have any other jobs currently running against this VM, feel free to delete this snapshot and re-run the backup job, this should enable CBT for this VM.

[0zzY]

Have i to delete also the backup files?
I'm using the reverse incremental method, and it had created a unique backup file for all the virtual machines (plus 3 incremental during the last 3 days).

or is it better one job for one vm?

[foggy]

No need to delete existing backups.

And here's a good discussion on how many VMs you should put in the job, please take a look: number of vms per job.

[dfowler]

Hello,

I am finding that Veeam takes significantly longer to backup a VM when there is an existing snapshot (VMware snapshot). The time it takes to backup will go from 20 minutes to 3.5 hours! I will be removing the snapshot as I no longer need it and hopefully the backup time will return to normal. Is this normal behaviour?

I would certainly appreciate any feedback on what others are seeing.

Thanks

Dave

[foggy]

David, due to existing VMware limitations, Veeam B&R cannot leverage VMware vSphere CBT for VMs that have existing snapshots at the moment of their first backup. Before running backup and replication jobs for a particular VM for the first time, it is recommended to delete all the snapshots to allow Veeam B&R to enable CBT on this VM automatically.

In case of existing snapshots, Veeam B&R triggers its proprietary algorithm to calculate blocks that should be transferred, but that requires reading the whole VM disks and could take significantly longer.

[dfowler]

Hi foggy, I appreciate the information. It took close to 4 hours to delete the snapshot (36 hours old) of the relatively small but dynamic VM (Blackerry Server). If Veeam B&R is going through the same IO processing to determine which blocks to transfer I can understand why the backup would take that much longer.

Thanks for the quick response

Dave

[foggy]

Actually, the process is not related to committing snapshots. We are using our proprietary changed block tracking engine instead of getting information about changed blocks from vSphere. Basically, the whole source VM image is scanned and hashes for all blocks are calculated to verify what blocks have been changed compared to the VM image stored in the backup file. That's why it takes much longer in this case.

[dfowler]

To close my part of the discussion and to share my results; after removing the VMware snapshot the Veeam B&R backup is under 30 minutes. Hopefully this is useful to others who may be trying to figure out why their backups are taking significantly longer than 'normal'. Great forum to share knowledge...thanks!

Dave

[vottak]

I faced the same problem "Changed Block Tracking Cannot Be Enabled: One or More Snapshots Present", I checked, but I have no pictures. How can this problem be solved?

VeeM offers such a solution to the problem, is it true in my case?

https://www.veeam.com/kb3169

Key Location: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
Value Name: VMware65CbtSnapshotCheckEnabled
Value Type: DWORD (32-bit) Value
Value Data: 0

[Gostev]

Please contact our customer support for assistance. Depending on the root cause, solutions are different.

[vottak]

Please contact our customer support for assistance. Depending on the root cause, solutions are different.

So maybe we will close the forum at all? It is necessary in order to receive help

[Gostev]

Apologies but I can't make sense of what you wrote.

You can receive help with environment-specific issues by contacting our Customer Support.

The purpose of this community is documented in the forum rules.