Re: Freebsd vs linux and hardware question

On Fri, Sep 19, 2003 at 03:48:35PM -0700, Dror Matalon wrote:
> > But hey, why are you asking this stuff? Don't you run Zapatec's stuff off a
> > huge SAN?
>
> It's not so Huge, out netapp is less than 200 Megs. But the real issue
> is that it works really well for small data sets but not for big ones.

BTW, he means 200 Gigs...

> We're working on a new application that will handle millions of rows.
> Currently the table size is half a gig and growing.
>
> On this type of application the netapp is slower than local disks. So
> we're thinking of setting up a new machine with plenty of power. I'm
> trying to figure out what the right configuration would be both in terms
> of the hardware and the OS.

the main problem is that the data is a time-series and now() isn't immutable
under Postgres 7.2 meaning that indices on a timestamp field don't work...ie.

select * from weblogs where ts > (now() - interval '7 days');

will always use a sequential scan since now() isn't cacheable. Worse yet,
there is no "immutable" flag for functions under 7.2 so we can't wrap now() in
a function marked immutable...(thanks to Stephan Szabo who explained this to
me a few months ago on sfpug)

a new database machine would allow us to use a newer version of Postgres which
could use an index and would avoid having to transfer an entire table from the
NAS for a sequential scan...(the network interface is a bottle-neck in that
case)

Aditya