[CentOS] LVM and Backups

Tue Sep 18 15:14:59 UTC 2018
Gordon Messmer <gordon.messmer at gmail.com>

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 

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.