Date: Tue, 10 Oct 2006 21:10:47 -0600 From: Scott Long <scottl@samsco.org> To: Doug Ambrisko <ambrisko@ambrisko.com> Cc: src-committers@FreeBSD.org, Kip Macy <kmacy@FreeBSD.org>, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org, Kip Macy <kmacy@fsmware.com>, Ceri Davies <ceri@submonkey.net>, John Birrell <jb@what-creek.com> Subject: Re: cvs commit: src/sys/conf Makefile.sun4v files.sun4v options.sun4v src/sys/sun4v/compile .cvsignore src/sys/sun4v/conf DEFAULTS GENERIC GENERIC.hints MAC Makefile NOTES src/sys/sun4v/include _bus.h Message-ID: <452C60B7.1000805@samsco.org> In-Reply-To: <200610102317.k9ANH46Z019000@ambrisko.com> References: <200610102317.k9ANH46Z019000@ambrisko.com>
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Doug Ambrisko wrote: > Kip Macy writes: > | > | The interface is not the same - can one buy an adapter? > > True that technically the interface is not the same. The SAS connector > spans the power supply and data port. SATA has separate data and > power. However, the mechanical spacing is the same except the SAS > drive does not have the gap to fit a separate power cable and separate > data cable. I've stuck several SATA drives in a SAS backplane > enclosure and Adaptec fan out cable. The mechanical interface > precludes a SAS driver plugged into a SATA controller but the > converse is not true. The bridge between the two connectors on SAS holds the pins for the second data channel that SAS supports. At a pure electrical and signaling level, the primary channel on SAS is compatible with the single channel on SATA. But for many technical and non-technical reasons, it's possible to plug a SATA disk into a SAS connector/controller, but not the other way around. > > Do you have a SATA drive to try? I've even mixed a SAS and SATA > drives on the same controller at the same time. I know a few > people using SATA on a SAS controller since SAS drives are harder > to come by. One of the promises of SAS was that you could combine the benefit of SAS infrastructure (multipathing, channel bonding, and out-of-the-box connectivity) with the cost effectiveness of SATA. Of course, that already existed with Fibre Channel, so the migration to SAS hasn't been as swift as many had hoped. > > Now Dell doesn't recommend mixing types but I've done it to > do some testing. Even though SATA and SAS are compatible at an electrical level, there is quite a bit of magic involved in making a SAS controller talk to a SATA disk. My guess is that Dell doesn't want you adding too many magic variables to the mix on such new technology. > > There is no adapter needed :-) > > I wish there was a SCSI drive to SAS interface like PATA drive to > SATA. Unfortunately my PATA adapter is not compliant and won't > just work with a SAS cable :-( I suppose that a PATA drive should work on a SAS controller if a SATA converter is used. It's also possible to put a Chevy Nova drive train into an Audi, given enough effort with a welding torch. I just wouldn't recommend it. Scott
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