Date: Sun, 18 Feb 1996 20:59:11 -0600 (CST) From: Bob Willcox <bob@luke.pmr.com> To: gibbs@freefall.freebsd.org (Justin T. Gibbs) Cc: freebsd-current@freefall.freebsd.org Subject: Re: Exabyte 8mm tape drive performance in -current? Message-ID: <199602190259.UAA02614@luke.pmr.com> In-Reply-To: <199602190132.RAA17788@freefall.freebsd.org> from "Justin T. Gibbs" at Feb 18, 96 05:32:57 pm
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Justin T. Gibbs wrote: > > >I have observed that the (read and write) performance of my 8mm > >Exabyte tape drives on my -current system runs roughly half of what > >it is on my 2.1-stable systems (100kb/sec vs. 200kb/sec). This is > >with both the NCR 810 and Adaptec 2940 adapters and using programs > >such as dump, tar, dd, team. The systems that I have compared have > >roughly the same hardware (both are 100MHz Pentiums). Performance > >on my Wangtek QIC-525 tape drive is about the same. Can anybody > >offer up an explaination of why this is and what might be done to > >fix it? > > I'd like to see if I can reproduce this on my system here. I have > both a -stable and -current boot configuration so I can test on > both. I'm using an Archive Python though, but if this is a generic > SCSI problem, it should still show up. Do you have a particular > benchmark script you'd like me to use? For the sake of simplicity, I have just been using dd. I dd a large (>40mb) file to the tape using a bs= specification of 32k or so. Dump, and tar show similar performance differences. My most recent run on my -current system looks like this: bob@han-p1 /usr/src> dd bs=32k if=cscope.out of=/dev/rst2 conv=sync 1369+1 records in 1370+0 records out 44892160 bytes transferred in 405 secs (110844 bytes/sec) and for this drive: bob@han-p1 /home/bob> mt -f /dev/rst2 status Present Mode: Density = 0x00 Blocksize = 512 bytes ---------available modes--------- Mode 0: Density = 0x00 Blocksize = 512 bytes Mode 1: Density = X3.136-1986 Blocksize = 512 bytes Mode 2: Density = X3.39-1986 Blocksize variable Mode 3: Density = X3.54-1986 Blocksize variable is what mt status looks like. Note that I am unable to change the blocksize to 0 (or anything else) with the mt blocksize command. For the equivalent operation on one of my 2.1-stable systems I get: bob@luke-pd /usr/src> dd bs=32k if=cscope.out of=/dev/rst1 conv=sync 1334+1 records in 1335+0 records out 43745280 bytes transferred in 213 secs (205376 bytes/sec) with an mt status of: bob@luke-pd /usr/src> mt -f /dev/rst1 status Present Mode: Density = 0x00 Blocksize variable ---------available modes--------- Mode 0: Density = 0x00 Blocksize variable Mode 1: Density = 0x00 Blocksize variable Mode 2: Density = 0x00 Blocksize variable Mode 3: Density = 0x00 Blocksize variable Thanks, -- Bob Willcox bob@luke.pmr.com Austin, TX
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