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@gmail.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@decibel.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@decibel.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?"
> >
>
