[CentOS] LVM and Backups
Gordon Messmer
gordon.messmer at gmail.com
Tue Sep 18 15:14:59 UTC 2018
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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