Date: Wed, 22 Jul 1998 23:39:29 -0400 (EDT) From: Mikhail Teterin <mi@aldan.algebra.com> To: questions@FreeBSD.ORG Subject: ccd questions Message-ID: <199807230339.XAA17390@rtfm.ziplink.net>
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Hello! I'm trying to do this under a day old -stable. There are four disks -- 2 2Gb and 2 4Gb -- involved. I set up two ccd mirroring disks 2Gb and 4Gb big each with different ileave numbers (from 2 to 6000, being powers of 2 and primes). Here are my problems: The 4 disks are on an ahc of their own with an idle tape-drive. I never tested both arrays at the same time. The 3 system disks are on a separate ahc. The machine has a single PPro-200 with 256Kb of cache, 128Mb of RAM, 192Mb of swap split evenly among three system drives. Performance: All four disks are different, so I do not expect "optimum" performance, but my results were still disappointing :( According to iozone benchmark, the write speed went down 50% compared to when using the disks by themselves -- without ccd. I would expect it to stay the same, really -- it is about 3.5Mb/sec and is far from saturating the 10Mb/s top of this SCSI interface. The ileave number does not seem to matter once it is above 32. The read speed is about the same -- according to `systat 1 -iostat' the data is read only from the first disk of an array -- I'd expect it to double as the things can be read in parallel from each of the drives. Again the ileave number does not seem to matter once it is above 32. Features/stability: I tried to create the third ccd to concatenate the two mirroring disks into one 6Gb big chunk. It "did not work" most of the time, and crashed the system once when it seemed to succeed and I started to newfs /dev/rccd2c Is this combination supposed to work at all? Thanks for your comments and suggestions! Yours, -mi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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