Re: UFS2 Snapshots and Postgres

On 6/25/2012 7:35 AM, Eduardo Morras wrote:

Hi everyone,

I'm using FreeBSD 9 for Postgres and want to know if these actions are safe for make a backup of the database:

a) call pg_start_backup('b1')
b) take an UFS2 snapshot of data files
c) call pg_stop_backup()
d) change to the snapshot dir and rsync/dd/dump/transfer it to backup file server

Is it safe to call pg_start_backup('b1',true)?

Thanks in advance

Snapshots are "safe" (but will result in a roll-forward on restart) IF AND ONLY IF the log data and database table spaces are all on the same snapshotted volume.

IF THEY ARE NOT then it will probably work 95% of the time, and the other 5% it will be unrecoverable.  Be very, very careful -- the snapshot must in fact snapshot ALL of the involved database volumes (log data included!) at the same instant.