Quiesce filesystems?

[rickardnobel]

I have two questions on this:

I have seen that this is an option when doing snapshots, is that recommended to do? Will it have any impact on performance on the VM?

Could "quiescing" be done any other way? In the Vmware official course (ICM) there is a note that all IO should be quiesced when growing a VMFS volume. Is that correct and if so, how do you do it?

[AntonVZhbankov · Accepted solution]

>I have seen that this is an option when doing snapshots, is that recommended to do?

Yes, of course. It forces guest OS to write all disk caches to disk, so you won't lose data.

>Will it have any impact on performance on the VM?

Quescing happens when snapshot is taken only, so it does not affect general performance.

>Could "quiescing" be done any other way?

Yes, for ex. Veeam Backup supports quescing file system via VSS instead of VMware Tools. And it really saves me, because one of my DC's suddenly started to refuse taking quiesced snapshots (reported to support).

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MCITP: SA, MCTS Hyper-V, VCP 3/4, VMware vExpert

http://blog.vadmin.ru

[rickardnobel]

>It forces guest OS to write all disk caches to disk, so you won't lose data.

Hello and thank you for your reply. I actually thought that quiesce meant "pausing" the file system, but it is what you write above? To force the guest OS internal disk cache to the virtual harddrive?

As for the growing of a VMFS datastore, do you know anything about doing quiscue then?

[AntonVZhbankov]

>I actually thought that quiesce meant "pausing" the file system, but it is what you write above? To force the guest OS internal disk cache to the virtual harddrive?

Yes, exactly. Since VMware ESX does not have any additional caching it means that all caches are written to physical storage.

>As for the growing of a VMFS datastore, do you know anything about doing quiscue then?

Quescing happens for guest OSes, so there is no need to do such a thing when VMFS datastore grows.

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MCITP: SA, MCTS Hyper-V, VCP 3/4, VMware vExpert

http://blog.vadmin.ru

[raedhei]

Hello ricnob,

I put a couple of links together which may help to understand the snapshot technology:

Using Snapshots To Manage Virtual Machines

Managing Existing Snapshots

Restoring Snapshots

Understanding Snapshots

Regards.

[frapposelli]

Yes, for ex. Veeam Backup supports quescing file system via VSS instead of VMware Tools. And it really saves me, because one of my DC's suddenly started to refuse taking quiesced snapshots (reported to support).

Actually IIRC since VI 3.5U2 VMware tools use VSS to quiesce the filesystem when taking a snapshot, at least on the OS that supports it (XP, 2003, 2008)

Ciao,

Fabio

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[AntonVZhbankov]

>since VI 3.5U2 VMware tools use VSS to quiesce the filesystem when taking a snapshot, at least on the OS that supports it (XP, 2003, 2008)

Yes, but for some strange reason one of my VMs cannot take quiesced snapshots anymore, while external VSS call from Veeam Backup works fine.

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MCITP: SA, MCTS Hyper-V, VCP 3/4, VMware vExpert

http://blog.vadmin.ru

[raedhei]

Hello AntonVZhbankov,

To troubleshoot VSS issues: Troubleshooting VSS

Shouldn't you find the problem, you may try to re-install the VMware Tools in custom mode without VSS. The VMware Tools will then use the SYNC driver. I have seen many times, that if you have more then one VSS driver installed, that it leads to problems. It depends how the vendor implements the VSS driver and whether this driver passed through those events which it won't handle, if it drops those events you are getting problems.

Regards.

[AntonVZhbankov]

raedhei, thanks for link, but I've already spen a month trying to figure out what's the problem, and VMware support confirmed it's a bug.

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MCITP: SA, MCTS Hyper-V, VCP 3/4, VMware vExpert

http://blog.vadmin.ru

[raedhei]

AntonVZhbankov, I'm sorry to hear that. Do you have a SR number? You may send it to via private message.

Regards.