On 03/09/2017 02:10 PM, Nathanaël Blanchet wrote: > > > Le 09/03/2017 à 12:10, Juan Hernández a écrit : >> On 03/09/2017 11:57 AM, Gianluca Cecchi wrote: >>> On Thu, Mar 9, 2017 at 11:39 AM, Nathanaël Blanchet <blanc...@abes.fr >>> <mailto:blanc...@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.cec...@gmail.com <mailto:gianluca.cec...@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. > Very useful piece of information, so does that mean memory save feature > not to be really useful? if so, it shouldn't be the default, so that vm > never go into pause state unusefully.
I didn't mean that saving memory isn't useful. It is very useful, for certain use cases. For the backup use case I think it is better to disable it. _______________________________________________ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users