Date: Tue, 27 Apr 2010 08:49:26 -0600 From: Scott Long <scottl@samsco.org> To: =?iso-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no> Cc: Alexander Motin <mav@freebsd.org>, FreeBSD-Current <freebsd-current@freebsd.org>, Richard Tector <richardtector@thekeelecentre.com>, freebsd-geom@freebsd.org Subject: Re: Switchover to CAM ATA? Message-ID: <70151EE0-AD49-4BB3-ADEB-68447A36D88A@samsco.org> In-Reply-To: <86och53tpl.fsf@ds4.des.no> References: <4BD06BD9.6030401@FreeBSD.org> <4BD099E6.6000402@FreeBSD.org> <4BD0A689.8000508@thekeelecentre.com> <4BD0ACD2.3040805@FreeBSD.org> <86och53tpl.fsf@ds4.des.no>
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On Apr 27, 2010, at 7:34 AM, Dag-Erling Sm=F8rgrav wrote: > Maxim Sobolev <sobomax@FreeBSD.org> writes: >> Richard Tector <richardtector@thekeelecentre.com> writes: >>> Could I also add that the removal of ataraid would affect those >>> users who dual-boot with Windows and rely on the psuedo-raid >>> provided by most Intel chipsets to be able to share the same pair of >>> disks. >> Well, this won't be a problem if we have GEOM classes that can >> understand metadata created by the ATA RAID BIOS(es). >=20 > Most pseudo-raid kit has nifty features like checksum offloading, > composite writes etc. which can improve performance considerably. You > can't access those from GEOM. If my "most" you mean "a small subset of vendors and products", then = yes, you're correct. For the vast remaining majority, all you get is a = special BIOS that can do striping and mirroring at boot. Sometimes that = special BIOS requires a special hook in the controller chip, which is = why you have ICHxxR vs ICHxx chips, for example. All the 'R' means is = that the silicon supports an external ROM. Scott
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