Re: Hardware estimation - Mailing list pgsql-general

On Thu, 7 Nov 2002, Steve Wolfe wrote:

> > Some of the "low end" 64 bit machines are not any more expensive than a
> > quad xeon can run.
>
>   Are you sure?  That might be the case if you use the most over-priced
> Xeon system you can find....
>
> >
> > A quad 1GHz Power4 with 8 gig ram, dual 36 Gig drives and all the
> fixings
> > goes for $44,000.  That's with 64 Meg L3 cache.
>
>    Wowee.  That's a lot of money.  You can build a quad Xeon with the same
> trimmings for a QUARTER of that price.  Will the Power4 provide four times
> the performance?

Well, with a maximum memory footprint of 64 Gigabytes, ALL of which can be
accessed by Postgresql if need be, it is quite likely to scale much
better.  Power4 64 bit CPUs are generally much faster at the same clock
rate than a P4 Xeon, at least in my limited experience.  The dual CPU
version of that box with only 4 gigs of ram is only about $26,000

This is also in a rack mount box with dual Hot swappable power supplies,
it can map out bad memory on the fly automatically, and can provide REAL 5
9 reliability.  32 MEGS of L3 cache, 6 megs of L2 cache, PER PROCESSOR.  A
backend connection with GIGs of data bandwidth per second.  An Intel based
box isn't even close to being in the same class.

> MB, chassis, triple power supply:  $4,000
> 4 x 2.4 GHz P4 Xeon CPU's:   $1,200
> 8 gigs RAM:  $3,000
> 2 x 15k 36 gig HDD:  $800
> ------------
> Total:  $9,000

Are these white box prices, or from someone like IBM or Dell?  The best
price I've seen with that configuration is about $20k. Is that ECC DDR
memory?

Keep in mind, that out of that 8 gigs of ram, only 1.5 or so is gonna be
available for Postgresql.  The rest will be system cache.  On a 64 bit
machine you can give as much as you want to the database.

>    Of course, the limitting factor in PG seems (to me, at least) to be
> I/O, not CPU power.  In a shared-bus sort of arrangement with 4
> processers, I think you'll generally run out of I/O (whether it be from
> the disks, memory,  or the CPU bus) long before you'll run out of CPU.

Actually, even when the CPUs are sitting at 5% load, having faster CPUs
tends to speed things up for postgresql, like maybe it's interrupt bound,
and faster CPUs can handle more interrupts a second.  Not sure why that
is, but I've definitely noticed it in my testing.

>    Once you get above the level of performance that an Intel or AMD system
> can provide, then your relative cost (based on performance) goes up pretty
> steeply - but since there aren't any other options, you're pretty much
> stuck with it.

Amen brother, amen.  But the 64 bit machines have room to grow.  If you
find that you need more memory, you can go up to 64 Gigs on many of them.

If you do wanna look at 64 bit systems that are Intel based then Dell
sells a quad Itanium for a fair price, but by the time you've  upped it to
8 gigs and a pair of 36 gig hard drives, and subtracted their gold star
on site support, the price is $46k.  For 4 800 MHz CPUs.

A Dell quad Xeon 1.6Gig with 8 gig ram is $29k  IBM is about $20k

Dropping down to a 2 way IBM Power4 series box drops you into the $26,000
range, which is very competetive to the Xeons.  And I wouldn't be at all
surprised to see a dual Power4 1GHz box outrun the quad Xeon, due to the
much faster I/O, and much larger L2 and L3 caches.