<stuff(at)opensourceonline(dot)com> writes:
> The caching appears to disappear overnight.
You've probably got cron jobs that run late at night and blow out your
kernel disk cache by accessing a whole lot of non-Postgres stuff.
(A nightly disk backup is one obvious candidate.) The most likely
solution is to run some cron job a little later to exercise your
database and thereby repopulate the cache with Postgres files before
you get to work ;-)
regards, tom lane