Re: Checkpoint cost, looks like it is WAL/CRC

On Wed, 2005-07-06 at 17:17 -0700, Joshua D. Drake wrote:
> >>Tom, I think you're the only person that could or would be trusted to
> >>make such a change. Even past the 8.1 freeze, I say we need to do
> >>something now on this issue.
> >
> >
> > I think if we document full_page_writes as similar to fsync in risk, we
> > are OK for 8.1, but if something can be done easily, it sounds good.
> >
> > Now that we have a GUC we can experiment with the full page write load
> > and see how it can be improved.
>
> Question, with this option if the power goes out will I just roll
> through the transaction logs like normal?

Most probably, yes. But:

> Or are we talking the
> potential to have to use something like pg_resetxlog or similar?

Potentially. Just depends on what sort of crash occurred...

> If it is just roll through the transaction logs then I have no problem
> with it, let the user decide the level of reliance they have. If it can
> cause actual, need to restore from backup level damage then it is a
> literall no go IMHO.

Well, it can't *cause* problems, but it doesn't solve them when they
occur, as the current design does. If crash recovery fails, and it may
do (and worst of all it might not fail when it should have) then you
will need to recover the database using PITR or a replication mechanism.

Best Regards, Simon Riggs