Date: Tue, 27 Apr 2010 16:16:29 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: Alexander Motin <mav@FreeBSD.org> Cc: Maxim Sobolev <sobomax@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: <86fx2h3rr6.fsf@ds4.des.no> In-Reply-To: <4BD6EDD6.8010403@FreeBSD.org> (Alexander Motin's message of "Tue, 27 Apr 2010 16:59:50 %2B0300") References: <4BD06BD9.6030401@FreeBSD.org> <4BD099E6.6000402@FreeBSD.org> <4BD0A689.8000508@thekeelecentre.com> <4BD0ACD2.3040805@FreeBSD.org> <86och53tpl.fsf@ds4.des.no> <4BD6EDD6.8010403@FreeBSD.org>
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Alexander Motin <mav@FreeBSD.org> writes: > Dag-Erling Sm=C3=B8rgrav <des@des.no> writes: > > 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. > Have you ever seen them documented? ISTR I got the info from sos@ at some point. I have several Promise cards lying around and was working onm RAID5 offloading, but I stopped when ZFS became usable. > Does the need to specifically handle dozens of incompatible > implementations with limited resources worth those (probably not > major) benefits? The details probably vary from controller to controller, but the capabilities are pretty much the same: perform the same write operation to several disks at once, split a write operation across several disks, compute and write parity. IIRC, composite writes are already supported but not used. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
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