On 3/17/06, Stewart Stremler <[EMAIL PROTECTED]> wrote:
> begin quoting Gregory K. Ruiz-Ade as of Fri, Mar 17, 2006 at 07:53:31PM
> -0800:
> > On Mar 17, 2006, at 10:09 AM, Dexter Filmore wrote:
> >
> > >If affordable, I go for SCSI.
> > >sATA = consumer cruft.
> >
> > SATA is actually pretty good in terms of reliability. WD and
> > Seagate, I think, offer "server-class" SATA drives (which just means
> > they have a lower MTBF and cost more).
>
> Poking around at Wikipedia, I get the impression that SATA requires
> one controller per disk (but it's only seven wires, so adding another
> controller to the ASIC is fairly trivial), with no daisy-chaining.
>
> Somewhere I found an assertion that SATA-II will support up to 15
> devices per controller, but it also talked about SATA port replication.
>
> > Besides, with modern SATA drives, price/performance-wise, you can buy
> > much more capacity in hot-spares than you can with SCSI.
>
> How much CPU time does a SATA disk require? SCSI can do device-to-device
> transfers with comparatively little CPU involvement; that, plus the number
> of devices you could hang off of a controller, makes SCSI much more
> attractive to me than IDE/ATA/PATA.
At the risk of sticking my neck out with insufficient information, I
will say that over many years of using SCSI I have yet to see any
application that takes advantage of the SCSI device-to-device
transfer. The closest thing to this is formatting a SCSI drive, where
everything is done with no interaction with the host adapter after the
initial command is transmitted.
As a curiosity matter, I find that the SATA disks on my Dell server
appear to Linux as SCSI. I don't know if this is a Fedora thing, or
universal.
> I'm not finding a lot of information about this so far tonight.
>
> > Six 300GB SATA drives (four in raid 5, two hot spare (is that raid6
> > with a hot spare?)) will likely be significantly cheaper than the
> > amount for SCSI drives you'd need to get a 900GB array with two hot
> > spares.
>
> Are these for comparable hardware? Another one of the web-pages
> asserted that (Enterprise-class? Server-class?) SCSI drives have
> stronger arms and better motors and suchlike, to better handle
> server-class loads.
carl
--
carl lowenstein marine physical lab u.c. san diego
[EMAIL PROTECTED]
--
[email protected]
http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
