[ovirt-users] oVirt VM backup and restore

[Gianluca Cecchi]

On Thu, Mar 9, 2017 at 11:39 AM, Nathanaël Blanchet <blanchet at abes.fr>
wrote:

>
>
> Le 09/03/2017 à 10:25, Gianluca Cecchi a écrit :
>
> On Wed, Mar 8, 2017 at 6:05 PM, Gianluca Cecchi <gianluca.cecchi at gmail.com
> > wrote:
>
>>
>>
>> NOTE: during the snapshot creation I see in web admin console the VM in
>> paused state and also not responsive in both console and ssh session.
>> After a couple of seconds it comes back and as a confirmation I see this
>> in its messages:
>>
>> Mar  8 17:38:57 T-ORACLE73 chronyd[616]: System clock wrong by 19.077230
>> seconds, adjustment started
>>
>> Is this expected?
>>
>>
>>
>>
> Possibly the default changed at some point in time, so that now it saves
> memory and so this implies pause of VM
>
> Saving memory is essential in some apàplications like DB, so you won't
> bypass vm pauses for such a stuff
>
>
Yes, indeed, the important thing is to have an option so that you can set
it True or False, depending on the VM you are saving, the application that
is running isnide it and the way you want to do backup of the application.
Nevertheless, RDBMS and also other applications often have some mechanism
to be "frozen in a consistent state" so that you can save what you have on
disk without need to save memory to have a consistent backup.
Oracle for example has functionality to be put in "backup mode" where you
issue "begin backup" before the snapshot and "end backup" right after
snapshot completion.
I see that POstgreSQL has similar functionality (not tested myself):
https://www.postgresql.org/docs/9.4/static/continuous-archiving.html#BACKUP-LOWLEVEL-BASE-BACKUP
and the same for other ones.

Gianluca
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