[ovirt-users] Info on live snapshot and agent interaction

[Yaniv Kaul]

On May 4, 2017 10:09 PM, "Michal Skrivanek" <michal.skrivanek at redhat.com>
wrote:


> On 4 May 2017, at 17:51, Gianluca Cecchi <gianluca.cecchi at gmail.com>
wrote:
>
> Hello,
> supposing to have a Linux VM with ovirt-guest-agent installed, during a
live snapshot operation it should be freeze of filesystems.
> Where to find confirmation of correct/successful interaction?

if it’s not successful there should be an event log message about that. And
prior to taking the snapshot a warning in red at the bottom of the dialog
(that check happens when you open the dialog, so it may not be 100%
reliable)

> /var/log/messages or agent log or other kind of files?

if you want to doublecheck then this is noticable in vdsm.log. First we try
to take the snapshot with fsfreeze, and only when it fails we take it again
without it.

> Are there any limitations on filesystems that support freeze? Is it
fsfreeze the command executed at VM OS level or any other low level command?

It’s a matter of Linux and Windows implementation, they both have an API
supporting that at kernel level. I’m not aware of filesystem limitations.


If you use Windows and the qemu-ga, it'd call VSS, which, if supported by
applications (ranging from Notepad to SQL server) will provide application
consistent snapshot.
Y.


Thanks,
michal

>
> Thanks,
> Gianluca
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