[CentOS] LVM and Backups

Mon Sep 17 20:12:29 UTC 2018
Gordon Messmer <gordon.messmer at gmail.com>

On 9/17/18 7:50 AM, Alessandro Baggi wrote:
> Running a backup I follow this steps:
> 1) Stop httpd
> 2) Create lvm snapshot on the dataset
> 3) Backup database
> 4) restart httpd (to avoid more downtime)
> 5) mount the snapshot and execute backup
> 6) umount and remove the snapshot
> I think that this could be fine (if not please correct me)

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.

Your sequence makes changes (step 3) after the snapshot is taken.  In 
that case, the backup that you made will not be a part of the snapshot.  
It also prolongs the time that httpd is down unnecessarily.

> Now when bacula performs the backup what happen if bacula are copying 
> a specifed file and this specified file is modified?

If bacula is backing up the content of the snapshot, then changes made 
in the running services won't affect it.  That's the purpose of the 
snapshot: it's static.

Are you using bacula's built-in snapshot support, or are you rolling 
your own?