Re: Snapshot backups

On Wed, Jul 31, 2013 at 08:24:46AM -0400, Tom Lane wrote:
> Alban Hertroys <haramrae@gmail.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 ...

Just to give the 10k mile answer, the WAL contains all database changes
that _might_ be lost due to file system changes during a base backup.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +