Re: [opensuse] Re: SATA / SAS controllers.

On 3/5/07, Anders Norrbring <lists@xxxxxxxxxxxx> wrote:
Greg Freemyer skrev:
> On 3/5/07, Anders Norrbring <lists@xxxxxxxxxxxx> wrote:
>> Right.. I'm actually looking at this
>> http://www.adaptec.com/en-GB/products/sas/raid/SAS-4800/
>
> Has anybody worked with any of the mix and match SATA / SAS controllers?
>
> They just seem weird to me, so I don't know what I think.
>
> ie. SATA uses the ATA command set. SAS uses the SCSI command set.
>
> Both SATA & SAS use the same cabling/voltages I believe, so there
> should not be an electrical issue, but I just have not seen any
> reports (good or bad) about controllers that can supposedly talk both
> ATA and SCSI.
>
> In Linux do they use a pure SCSI driver?
>
> BTW: 3ware uses a pure SCSI driver even for it s PATA controller line,
> so I don't have an issue with that, just lots of unknowns from my
> perspective.
>
> Greg

As I've understood, the Adaptec SAS RAID controllers use the aacraid
driver in Linux, which we all have already.. ;) They also provide some
extra stuff for their HBAs. But then again, I can be terribly wrong, I
haven't used SAS HBAs from Adaptec before, just SCSI.

I'm not sure I understand what you mean by "mixing" SAS and SATA? On a
SAS HBA, you can hook up SATA drives natively, and SAS drives as well.
However, mixing both types of drives on the same channel is asking for
problems..


I'm a newbie with this technology, but AIUI you have a sata/sas
connector on the controller. If you connect it to a SATA drive the
controller figures it out and all communications uses the ATA command
set.

OTOH, if instead you connect the connector up to a SAS drive, then the
controller figures that out and all communications is with the SCSI
command set.

So if the aacraid scsi driver is used then for SAS drives, the
controller is basically just passing the SCSI commands straight thru,
but for a SATA drive the controller is doing a SCSI to ATA translation
before sending it out. Again I have nothing bad to say about that, I
just don't have any first hand experience and I haven't seen any
postings that I can recall.

Greg
--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century
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