Re: Index Scans become Seq Scans after VACUUM ANALYSE

Curt Sampson <cjs@cynic.net> writes:
> This should also allow us to disable completely the ping-pong writes
> if we have a disk subsystem that we trust.

If we have a disk subsystem we trust, we just disable fsync on the
WAL and the performance issue largely goes away.

I concur with Bruce: the reason we keep page images in WAL is to
minimize the number of places we have to fsync, and thus the amount of
head movement required for a commit.  Putting the page images elsewhere
cannot be a win AFAICS.

> Well, whether or not there's a cheap way depends on whether you consider
> fsync to be cheap. :-)

It's never cheap :-(
        regards, tom lane