Date: Thu, 04 May 2000 12:22:53 -0700 From: Mike Smith <msmith@freebsd.org> To: vallo@matti.ee Cc: Mike Smith <msmith@freebsd.org>, Parag Patel <parag@cgt.com>, freebsd-stable@freebsd.org Subject: Re: How good is AMI MegaRAID support? Message-ID: <200005041922.MAA01426@mass.cdrom.com> In-Reply-To: Your message of "Thu, 04 May 2000 21:06:35 %2B0200." <20000504210635.A8681@myhakas.matti.ee>
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> On Sat, Apr 29, 2000 at 09:31:50PM -0700, Mike Smith <msmith@freebsd.org> wrote: > > > > Out of curiosity, how would a PCI-RAID (SCSI) adapter compare with > > > vanilla PCI-SCSI cards and vinum? It seems to me that the host CPU(s) > > > are much faster than the processors on the PCI-SCSI adapters. Or are > > > both of these "fast-enough" and thus performance differences are largely > > > an irrelevent consideration? (They both have similar software issues > > > but I suspect vinum is easier to debug. :) > > > > All other things being equal, software RAID is going to be faster. (ie. > > same disks, same # of SCSI channels, etc.) The hardware solution's sell > > there is: > > > > - better support/functionality (enclosure management, etc.) > > - better survivability (battery-backed cache) > > > > Plus you get a stack of SCSI channels onboard the card. > > Are you sure? I think the upcoming IBM ServeRaid version 4 adapters will > have PowerPC 750 processor which outperforms current host processors > easily? I'd like to see it take on eg. a 1GHz K7 or a 4-way 800MHz PIII/Xeon box. > Anyway I think for degraded mode you'll definitely need separate > processing unit to offload parity calculations from host processor, else > the system will calculate parity not service users. That's theory, of > course, but it seems so obvious. Am I missing something? All this > discussion seems quite unnecessary in that light for me. Having dedicated hardware for offloading this sort of work is nice when the host is saturated. If it's not, then it's unnecessary. Your call; personally I like the hardware. -- \\ Give a man a fish, and you feed him for a day. \\ Mike Smith \\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org \\ and he'll hate you for a lifetime. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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