Date: Mon, 3 Oct 2005 09:55:49 +0200 From: Patrick Proniewski <patpro@patpro.net> To: Eric Anderson <anderson@centtech.com> Cc: freebsd-performance@freebsd.org, "=?ISO-8859-1?Q? Arne_\"W=F6rner\" ?=" <arne_woerner@yahoo.com> Subject: Re: dd(1) performance when copiing a disk to another Message-ID: <618C4F4D-A3F6-4F34-9352-C7C86DC1DD9E@patpro.net> In-Reply-To: <43401C62.2040606@centtech.com> References: <20051002170446.78674.qmail@web30303.mail.mud.yahoo.com> <43401C62.2040606@centtech.com>
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Hi Arne and Eric, >>> # atacontrol mode 0 >>> Master = BIOSPIO >>> Slave = BIOSPIO >> Hmm... 0 seems to be the wrong ata... Thats why the output does >> not fit to SATA drives, I think... oups... I'll have to do it again with channels 2 and 3 >>> # dd if=/dev/ad4 of=/dev/null bs=1m count=1000 >>> 1000+0 records in >>> 1000+0 records out >>> 1048576000 bytes transferred in 17.647464 secs (59417943 >>> bytes/sec) >> That seems to be 2 or about 2 times faster than disc->disc >> transfer... But still slower, than I would have expected... >> SATA150 sounds like the drive can do 150MB/sec... As Eric pointed out, you just can"t reach 150 MB/s with one disk, it's a technological maximum for the bus, but real world performance is well bellow this max. In fact, I've though I would reach about 50 to 60 MB/s. >>>> (Maybe you could find a way to copy /dev/zero to /dev/ad6 >>>> without destroying the previous work... :-)) >>> >>> well, not very easy both disk are the same size ;) >> I thought of the first 1000 1MB blocks... :-) damn, I misread this one... :) I'm gonna try this asap. > Instead of dd, why not use gmirror? I had no idea gmirror exists, but I'll continue with dd. It's a one time experiment. > Have you tried a smaller block size? What does 8k, 16k, or 512k do > for you? There really isn't much room for improvement here on a > single device. nop, I'll try one of them, but I can't do many experiments, the box is in my living room, it's a 1U rack, and it's VERY VERY noisy. My girlfriend will kill me if it's running more than an hour a day :)) Pat
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