Re: does database shut down cleanly when WAL device fails?

Tom Lane wrote:
> Brandon Craig Rhodes <brandon(at)rhodesmill(dot)org> writes:
> > And the disputed point:
>
> > - If the drive holding the WAL fails, then the database engine
> > will shut down cleanly by writing everything in RAM out to
> > the real database tables, and no data will be lost.
>
> Whoever claimed that has no familiarity with the code at all, and no
> understanding of the basic WAL rule: write to the log BEFORE you write
> data.
>
> In point of fact, loss of the WAL drive will mean a database PANIC stop
> and probably a corrupt data area afterwards, since there'd be no
> guarantee that related page updates had all made it to disk.

Also the WAL files might be recyled at each checkpoint, which is at
least every five minutes, so pg_xlog will not contain all the WAL files
from the backup, unless you are using point-in-time recovery --- this
might be where you got confused.

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