Date: Fri, 17 Dec 1999 11:54:42 -0500 (EST) From: David Gilbert <dgilbert@velocet.ca> To: Brad Knowles <blk@skynet.be> Cc: David Gilbert <dgilbert@velocet.ca>, Mike Smith <msmith@FreeBSD.ORG>, freebsd-current@FreeBSD.ORG Subject: Re: AMI MegaRAID datapoint. Message-ID: <14426.27346.393029.804411@trooper.velocet.net> In-Reply-To: <v04220809b4801618502e@[195.238.1.121]> References: <14425.2778.943367.365945@trooper.velocet.net> <199912162354.PAA02071@mass.cdrom.com> <14426.20641.329657.464545@trooper.velocet.net> <v04220809b4801618502e@[195.238.1.121]>
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>>>>> "Brad" == Brad Knowles <blk@skynet.be> writes: Brad> At 10:02 AM -0500 1999/12/17, David Gilbert wrote: >> Well... it's RAID-5 across the same 8 drives with all 8 drives on >> one LVD chain (same configuration as the other test). I have tried >> the 128k stripe, but it was slower than the default 64k stripe. Brad> One of the lessons I learned from Greg was that, when dealing Brad> with RAID implementations in hardware, you should usually take Brad> their "native" stripe size, since that's the one that will Brad> usually perform best. Brad> It's only when you do software RAID (e.g., vinum) that you can Brad> choose larger or smaller stripe sizes with a reasonable Brad> expectation that you will get the particular performance Brad> enhancement that you're hoping for. Another thing that I find very different betweent he vinum software RAID-5 and the hardware I've tried (I've used both the DPT and the MegaRAID controllers) that the latency of a command can be incredible on the hardware raid. If you type (for instance) 'du -ks foo' where foo is a big directory on the hardware raid, and then press CTRL-C, it can take 10 to 15 seconds to come back (I'm assuming that this is queued I/O requests). Dave. -- ============================================================================ |David Gilbert, Velocet Communications. | Two things can only be | |Mail: dgilbert@velocet.net | equal if and only if they | |http://www.velocet.net/~dgilbert | are precisely opposite. | =========================================================GLO================ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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