[ovirt-users] oVirt VM backup and restore

[Maton, Brett]

Good point

On 9 March 2017 at 11:10, Juan Hernández <jhernand at redhat.com> wrote:

> On 03/09/2017 11:57 AM, Gianluca Cecchi wrote:
> > On Thu, Mar 9, 2017 at 11:39 AM, Nathanaël Blanchet <blanchet at abes.fr
> > <mailto: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 <mailto: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
> >
>
> Just wanted to add that freezing activity is not only important for
> databases, but also for plain file systems. In order to do a consistent
> backup it is important to freeze the file systems before creating a live
> snapshot, and thaw it afterwards. oVirt does that automatically, but
> only if the guest agent is installed and running. So, remember to have
> the guest agent installed and running in the virtual machines that you
> plan to backup using this mechanism.
>
>
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