Re: hanging for 30sec when checkpointing

On Tue, 10 Feb 2004, Tom Lane wrote:

> "scott.marlowe" <scott.marlowe@ihs.com> writes:
> >> Unfortunately not --- at checkpoint time, the constraint goes the other
> >> way.  We have to be sure all the data file updates are down to disk
> >> before we write a checkpoint record to the WAL log.  So you can still
> >> get screwed if the data-file drive lies about write completion.
>
> > Hmmm.  OK.  Would the transaction size be an issue here?  I.e. would small
> > transactions likely be safer against corruption than large transactions?
>
> Transaction size would make no difference AFAICS.  Reducing the interval
> between checkpoints might make things safer in such a case.
>
> > I ask because most of the testing I did was with pgbench running 100+
> > simos (on a -s 100 pgbench database) and as long as the WAL drive was
> > fsyncing correctly, the database survived.
>
> Did you try pulling the plug immediately after a CHECKPOINT command
> completes?  You could test by manually issuing a CHECKPOINT while
> pgbench runs, and yanking power as soon as the prompt comes back.

I will try that.  Thanks for the tip.  I'll let you know how it works
out.