Re: Snapshot backups

Thank you Tom! This is what I was after!

So, to get this straight in my head.

- pg_start_backup forces a checkpoint and writes the information from
this checkpoint to the backup_label file
- <snapshot>
- pg_stop_backup removes the backup_label file
- <disaster!>
- <restore snapshot>
- Database starts and determines where to start WAL replay from the
backup_label NOT from pg_control (as usual)

Cheers,
James

James Sewell
PostgreSQL Team Lead / Solutions Architect
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On Wed, Jul 31, 2013 at 10:24 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Alban Hertroys <haramrae(at)gmail(dot)com> writes:
> > That begs the question what happens in case of a crash or (worse) a
> partial crash when multiple file systems are involved.
>
> As long as the OS+hardware honors the contract of fsync(), everything's
> fine. If the storage system loses data that it claims to have fsync'd to
> stable storage, there's not much we can do about that, except recommend
> that you have a backup plan.
>
> In practice, the more complicated your storage infrastructure is, the more
> likely it is to have bugs ...
>
> regards, tom lane
>

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