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?"
>
