[CentOS] LVM and Backups

Wed Sep 19 06:55:25 UTC 2018
Alessandro Baggi <alessandro.baggi at gmail.com>

Il 18/09/2018 17:14, Gordon Messmer ha scritto:
> On 9/17/18 11:38 PM, Alessandro Baggi wrote:
>> Il 17/09/2018 22:12, Gordon Messmer ha scritto:
>>> That doesn't look right.  It should look more like 1) stop or freeze 
>>> all of the services (httpd and database), 2) make the snapshot, 3) 
>>> start or thaw all of the services, 4) mount the snapshot, 5) back up 
>>> the data, 6) remove the snapshot.
>> About database setup I perform backups via pg_dump so how the snapshot 
>> affects pgsql database? What your suggestion I must perform database 
>> backup copying only filesystem file and not pgsql.sql database dump?
> If you want a plain-text dump of the DB, you can do that before the LVM 
> snapshot sequence: 1) pg_dump, 2) stop or freeze all of the services 
> (httpd and database), 3) make the snapshot, 4) start or thaw all of the 
> services, 5) mount the snapshot, 6) back up the data, 7) remove the 
> snapshot.
> Typically, the reason you want to use snapshots for the backup is that 
> you don't need to do pg_dump to get a consistent DB backup, though. 
> pg_dump style backups are extremely slow to restore.  If you freeze the 
> DB, make a snapshot, and thaw, you can make a safe, consistent backup of 
> the DB files directly, and restore in minimal time.
>>> Are you using bacula's built-in snapshot support, or are you rolling 
>>> your own?
>> No I'm using pre/post job script where I have lvm commands to create 
>> and destroy snapshot volume.
> I really recommend using a ready-made process rather than rolling your 
> own.  Bacula has snapshot support.  Alternately, my project can manage 
> snapshots and handle freezing / thawing PostgreSQL services.  I think 
> it's a better option than Bacula's, but either is better than 
> reinventing this wheel.
> https://bitbucket.org/gordonmessmer/dragonsdawn-snapshot
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Thank you for the suggestion.

I don't know why I considered pg_dump better then filesystem backup. At 
this moment I prefer pg_dump because in this mode I can restore data on 
different version of postgresql. With filesystem dump I can restore only 
for a specific version. Is right?

I will give a try.

Thank you again for suggestions.