Date: Mon, 9 Oct 1995 16:52:25 -0400 (EDT) From: Chuck Robey <chuckr@eng.umd.edu> To: Stefan Esser <se@zpr.uni-koeln.de> Cc: hackers@freebsd.org Subject: Re: VLB Disk Controllers Message-ID: <Pine.SUN.3.91.951009164607.13868A@mocha.eng.umd.edu> In-Reply-To: <199510091957.AA03237@Sysiphos>
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On Mon, 9 Oct 1995, Stefan Esser wrote: > On Oct 7, 22:33, Chuck Robey wrote: > } Subject: Re: VLB Disk Controllers > } On Sun, 8 Oct 1995, Stefan Esser wrote: > } > } > Something I just noticed is the big difference > } > in results I get using /dev/rsd0 vs. /dev/rsd0a: > } > > } > # disklatency /dev/rsd0 > } > Command overhead is 719 usec (time_4096 = 1198, time_8192 = 1677) > } > transfer speed is 8.55617e+06 bytes/sec > } > > } > # disklatency /dev/rsd0a > } > Command overhead is 807 usec (time_4096 = 1272, time_8192 = 1738) > } > transfer speed is 8.80588e+06 bytes/sec > } > } I just did that 10 times in a row with my 2842, and reading differing > } over a 2:1 range. I think there's some windage here that makes your > } comparison suspect. Try it a few tries in a row on the same drive. [many test results deleted, showing little variance] > Seems quite consistent over any number of tests ... [more deletions] > Interesting ... Would have expected /dev/zero to be > faster in any way ! > > (BTW: Reading /dev/zero on the Sparc10 has only 54 us > overhead. Seems they are good for something after all :-) OK, I've been watching the posted results, many have as little variance as yours, but many (where multiple runs were shown) had the huge variance mine had. Would like to know why my checks to /dev/sd0 are all over the board, when checks to rsd0 are fairly stable at 1180-1190. ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 9120 Edmonston Ct #302 | Greenbelt, MD 20770 | I run Journey2 and n3lxx, both FreeBSD (301) 220-2114 | version 2.2 current -- and great FUN! ----------------------------+-----------------------------------------------
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