Re: How to improve db performance with $7K?

Ok - I take it back - I'm reading through this now, and realising that
the reviews are pretty clueless in several places...

On Apr 6, 2005 8:12 PM, Alex Turner <armtuk(at)gmail(dot)com> wrote:
> Ok - so I found this fairly good online review of various SATA cards
> out there, with 3ware not doing too hot on RAID 5, but ok on RAID 10.
>
> http://www.tweakers.net/reviews/557/
>
> Very interesting stuff.
>
> Alex Turner
> netEconomist
>
> On Apr 6, 2005 7:32 PM, Alex Turner <armtuk(at)gmail(dot)com> wrote:
> > I guess I'm setting myself up here, and I'm really not being ignorant,
> > but can someone explain exactly how is SCSI is supposed to better than
> > SATA?
> >
> > Both systems use drives with platters. Each drive can physically only
> > read one thing at a time.
> >
> > SATA gives each drive it's own channel, but you have to share in SCSI.
> > A SATA controller typicaly can do 3Gb/sec (384MB/sec) per drive, but
> > SCSI can only do 320MB/sec across the entire array.
> >
> > What am I missing here?
> >
> > Alex Turner
> > netEconomist
> >
> > On Apr 6, 2005 5:41 PM, Jim C. Nasby <decibel(at)decibel(dot)org> wrote:
> > > Sorry if I'm pointing out the obvious here, but it seems worth
> > > mentioning. AFAIK all 3ware controllers are setup so that each SATA
> > > drive gets it's own SATA bus. My understanding is that by and large,
> > > SATA still suffers from a general inability to have multiple outstanding
> > > commands on the bus at once, unlike SCSI. Therefore, to get good
> > > performance out of SATA you need to have a seperate bus for each drive.
> > > Theoretically, it shouldn't really matter that it's SATA over ATA, other
> > > than I certainly wouldn't want to try and cram 8 ATA cables into a
> > > machine...
> > >
> > > Incidentally, when we were investigating storage options at a previous
> > > job we talked to someone who deals with RS/6000 storage. He had a bunch
> > > of info about their serial controller protocol (which I can't think of
> > > the name of) vs SCSI. SCSI had a lot more overhead, so you could end up
> > > saturating even a 160MB SCSI bus with only 2 or 3 drives.
> > >
> > > People are finally realizing how important bandwidth has become in
> > > modern machines. Memory bandwidth is why RS/6000 was (and maybe still
> > > is) cleaning Sun's clock, and it's why the Opteron blows Itaniums out of
> > > the water. Likewise it's why SCSI is so much better than IDE (unless you
> > > just give each drive it's own dedicated bandwidth).
> > > --
> > > Jim C. Nasby, Database Consultant decibel(at)decibel(dot)org
> > > Give your computer some brain candy! www.distributed.net Team #1828
> > >
> > > Windows: "Where do you want to go today?"
> > > Linux: "Where do you want to go tomorrow?"
> > > FreeBSD: "Are you guys coming, or what?"
> > >
> >
>