Re: Serial ATA: SCSI Replacement?

On 09/12/06 10:54 pm Robert Han*** wrote:

SCSI seems to have gone away for home users... and I donated all my old
SCSI cables, cards, and a drive or two to the trash a couple weeks ago.

But it raised a question for me.

Seems like one of SCSI's claims to fame was unloading the work of disc
access from the CPU to the SCSI controller.

Not really.. The CPU usage of SCSI was sometimes slightly lower, but there's not been a huge difference since DMA became commonplace on IDE/ATA almost 10 years ago.

In server-type use the better command queueing ability of SCSI made some performance difference (NCQ does essentially the same thing on SATA). Most of the performance advantage of SCSI drives had nothing to do with the interface at all - the drives were usually higher spindle RPM and faster in themselves.

But, according to a Seagate white paper, their SCSI drives are designed for multi-drive systems whereas their IDE ones are not. This includes remaining cool when mounted close together and not causing or being susceptible to harmful vibrations among the drives. The SCSI drives aren't simply the same drive spinning at a higher speed and with a different interface.

There's also the ability to have 15 drives on a SCSI bus.

And don't forget hot-swappability.

Another advantage of SCSI over IDE used to be that SCSI drives normally had a 5-year warranty while IDE drive warranties were commonly only 1 year. But Seagate's IDE drives (and *only* Seagate's, AFAIK) now have the 5-year warranty too.

Given that SCSI is then and Serial ATA is now; does Serial ATA fulfill
that function?

Well, yes, but that is nothing special. The replacement for SCSI is actually going to be SAS (Serial Attached SCSI) which is a superset of SATA and supports some additional features.

I've seen the announcements of SAS, but do the drives actually exist yet?

Perce
.

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