Re: How to make a REALLY FAST db server? - Mailing list pgsql-general

""Steve Wolfe"" <steve@iboats.com> wrote in message
news:002c01c13d59$528f6f00$50824e40@iboats.com...
> > >   (As an aside, one person was in a heated argument about how much
> cheaper
> > > IDE was than SCSI.  I got on pricewatch, found some prices, and would
> have
> > > been able to put together a very fast SCSI system for the same price
> as
> > > his IDE array.)
> >
> > That's nuts: SCSI disks cost a lot more than comparable IDE disks.
>
>    But it's true.  For cutting-edge SCSI disks, the price is quite high.
> If you look, though, you can find places trying to get rid of "last-year's
> model" for very low prices, and you can sometimes find very good
> performers like that.  I picked up some 10K IBM drives with 4 ms access
> times for something like $125 or $150 each.   If you'd like to find
> "comparable" IDE drives for that price, you're out of luck, as IDE doesn't
> have a 160 MB/sec bus, and I don't think you'll find any IDE drives with
> that low of access times anywhere.

What I said: "SCSI disks cost a lot more than comparable IDE disks."

What you said: "No, because I found some cheap SCSI disks that
don't have comparable IDE models."

What you say may be true, but it does not in any way refute what
I said about comparing prices between comparable SCSI and
IDE models. My statement only operates in the domain where
there ARE comparable models.

SCSI disks cost more than comparable IDE disks. An example:
(prices from pricewatch)
7200rpm 36.4gb SCSI disk $191
7200rpm 40.0gb ATA100 disk $97.

Here the ratio is juts below 2:1, which is cheaper than the last time
I made the survey, when the ratio was about 2.5:1.

These days, there aren't many SCSI drives below 10000 rpm, and
there aren't any (?) IDE drives above 7200 rpm, so making the
comparison is harder. I suspect that IDE is taking over the low
end and SCSI is losing market share all around. I'd guess the
reduced demand is responsible for the declining prices.

As far as the first contention, about arrays:

IDE array
3ware 7410 $265
4x WD100BB drives $254 ea
total: $1281, uses 4 drive bays

SCSI array
(cheapest $/gb on scsi is had with smaller drives. You
can run the numbers with larger drives but it's more expensive.)
adaptec 131-u2 RAID $316
11x IBM Ultrastar 36XP $191ea
total: $2417.

Both arrays will saturate your bus. The scsi array will probably
perform marginally better, if only because it has more drives.


>    (Not to mention the fact that IDE drives only do well when a single
> process is accessing them.  SCSI, having been designed from the gound up
> for this sort of thing, does much better when you're hitting the disks
> from several places at once.)


Do you have any hard data to back this up? I'd be interested.

Usually when this question is asked, the response is "well,
I've run a lot of servers, and they just seem faster." But I'm
only interested in hard data.



Marshall