<div dir="ltr">Good point<br></div><div class="gmail_extra"><br><div class="gmail_quote">On 9 March 2017 at 11:10, Juan Hernández <span dir="ltr"><<a href="mailto:jhernand@redhat.com" target="_blank">jhernand@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On 03/09/2017 11:57 AM, Gianluca Cecchi wrote:<br>
> On Thu, Mar 9, 2017 at 11:39 AM, Nathanaël Blanchet <<a href="mailto:blanchet@abes.fr">blanchet@abes.fr</a><br>
</span><span class="">> <mailto:<a href="mailto:blanchet@abes.fr">blanchet@abes.fr</a>>> wrote:<br>
><br>
><br>
><br>
> Le 09/03/2017 à 10:25, Gianluca Cecchi a écrit :<br>
>> On Wed, Mar 8, 2017 at 6:05 PM, Gianluca Cecchi<br>
</span><div><div class="h5">>> <<a href="mailto:gianluca.cecchi@gmail.com">gianluca.cecchi@gmail.com</a> <mailto:<a href="mailto:gianluca.cecchi@gmail.com">gianluca.cecchi@gmail.<wbr>com</a>>> wrote:<br>
>><br>
>><br>
>><br>
>> NOTE: during the snapshot creation I see in web admin console<br>
>> the VM in paused state and also not responsive in both console<br>
>> and ssh session.<br>
>> After a couple of seconds it comes back and as a confirmation<br>
>> I see this in its messages:<br>
>><br>
>> Mar 8 17:38:57 T-ORACLE73 chronyd[616]: System clock wrong by<br>
>> 19.077230 seconds, adjustment started<br>
>><br>
>> Is this expected?<br>
>><br>
>><br>
>><br>
>><br>
>> Possibly the default changed at some point in time, so that now it<br>
>> saves memory and so this implies pause of VM<br>
> Saving memory is essential in some apàplications like DB, so you<br>
> won't bypass vm pauses for such a stuff<br>
><br>
><br>
> Yes, indeed, the important thing is to have an option so that you can<br>
> set it True or False, depending on the VM you are saving, the<br>
> application that is running isnide it and the way you want to do backup<br>
> of the application.<br>
> Nevertheless, RDBMS and also other applications often have some<br>
> mechanism to be "frozen in a consistent state" so that you can save what<br>
> you have on disk without need to save memory to have a consistent backup.<br>
> Oracle for example has functionality to be put in "backup mode" where<br>
> you issue "begin backup" before the snapshot and "end backup" right<br>
> after snapshot completion.<br>
> I see that POstgreSQL has similar functionality (not tested myself):<br>
> <a href="https://www.postgresql.org/docs/9.4/static/continuous-archiving.html#BACKUP-LOWLEVEL-BASE-BACKUP" rel="noreferrer" target="_blank">https://www.postgresql.org/<wbr>docs/9.4/static/continuous-<wbr>archiving.html#BACKUP-<wbr>LOWLEVEL-BASE-BACKUP</a><br>
> and the same for other ones.<br>
><br>
> Gianluca<br>
><br>
<br>
</div></div>Just wanted to add that freezing activity is not only important for<br>
databases, but also for plain file systems. In order to do a consistent<br>
backup it is important to freeze the file systems before creating a live<br>
snapshot, and thaw it afterwards. oVirt does that automatically, but<br>
only if the guest agent is installed and running. So, remember to have<br>
the guest agent installed and running in the virtual machines that you<br>
plan to backup using this mechanism.<br>
<div class="HOEnZb"><div class="h5"><br>
<br>
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</div></div></blockquote></div><br></div>