Date: Sun, 8 Oct 1995 19:16:21 +1000 From: Bruce Evans <bde@zeta.org.au> To: hackers@freebsd.org, pete@puffin.pelican.com Subject: Re: VLB Disk Controllers Message-ID: <199510080916.TAA26226@godzilla.zeta.org.au>
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>old seagate? 1.6g drive (some of these were IBM): >ringworld:6# ./disklatency /dev/rdsk/dks0d6s0 >Command overhead is 16650 usec (time_4096 = 16648, time_8192 = 16646) >transfer speed is -2.67712e+09 bytes/sec >old seagate? 1.6g drive (some of these were IBM): >ringworld:7# ./disklatency /dev/rdsk/dks0d6s6 >Command overhead is 16671 usec (time_4096 = 16668, time_8192 = 16664) >transfer speed is -1.2812e+09 bytes/sec >Among other things the 1.6 drive has a problem; maybe it's doing recals... >(though it doesn't have a problem with iozone so something else may be >wrong like relocated blocks near the beginning of the partitions or >something such) >(and it shows a problem in the program's checking of out-of-range >data; somehow I doubt that the rate is really negative...) >... >These drives are all (except maybe the old 1.6g drive?) variable-frequency >so one end or the other of the seek range should have faster data-transfer. No, the program is supposed to be transferring data out of the drive's cache, so its speed should be independent of the drive position unless the cache is smaller than 8K or is otherwise braindamaged. Apparently the seacrates' caches are braindamaged :-). They show that SGI SCSI is 6 times slower than slow IDE :-). Bruce
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