Re: UFS2 Snapshots and Postgres

Karl Denninger <karl@xxxxxxxxxxxxx> · Mon, 25 Jun 2012 08:16:53 -0500



    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.

    
    -- 

      Karl Denninger

      karl@xxxxxxxxxxxxx

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