On Mon, Jun 25, 2012 at 4:34 PM, Eduardo Morras <nec556@xxxxxxxxxx> wrote:
> At 15:16 25/06/2012, you wrote:
>
>
>> 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.
>
>
> Even if i do a pg_start_backup()? I thought it set db data/ files in a
> consistent state and puts in wal files the new transactions and apply them
> when call pg_stop_backup().
>
> I must do it other way then :(
No, if you use pg_start_backup() and pg_stpo_backup() (and verify all
their return codes...), *and* you use log archiving using
archive_command, then snapshots are safe even if they are on different
filesystems.
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
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