> > I have a postgresql 7.4.8-server with 4 GB ram.
> > #effective_cache_size = 1000    # typically 8KB each
> >
> > This is computed by sysctl -n vfs.hibufspace / 8192 (on FreeBSD). So I
> > changed it to:
> >
> > effective_cache_size = 27462    # typically 8KB each
>
> Apparently this formula is no longer relevant on the FreeBSD systems as
> it can cache up to almost all the available RAM. With 4GB of RAM, one
> could specify most of the RAM as being available for caching, assuming
> that nothing but PostgreSQL runs on the server -- certainly 1/2 the RAM
> would be a reasonable value to tell the planner.
>
> (This was verified by using dd:
> dd if=/dev/zero of=/usr/local/pgsql/iotest bs=128k count=16384 to create
> a 2G file then
> dd if=/usr/local/pgsql/iotest of=/dev/null
>
> If you run systat -vmstat 2 you will see 0% diskaccess during the read
> of the 2G file indicating that it has, in fact, been cached)

Thank you for your reply. Does this apply to FreeBSD 5.4 or 6.0 on
amd64 (or both)?

regards
Claus

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