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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!nntp.coast.net!chi-news.cic.net!newsfeed.internetmci.com!in1.uu.net!xplor!news.us.world.net!ns2.mainstreet.net!bug.rahul.net!a2i!rahul.net!a2i!dandelion.com!not-for-mail From: "Leonard N. Zubkoff" <lnz@dandelion.com> Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: CDROM Changers Date: 20 Dec 1995 02:47:31 -0800 Organization: Dandelion Digital Lines: 23 Sender: lnz@dandelion.com Message-ID: <4b8pk3$52@kelewan.dandelion.com> References: <BILLW.95Dec8181411@puli.cisco.com> <4b2q1p$796@kelewan.dandelion.com> <4b5guj$g02@elliot.ics.uci.edu> <4b5t4s$9qv@kelewan.dandelion.com> <4b8m5g$la6@elliot.ics.uci.edu> NNTP-Posting-Host: dandelion.com NNTP-Posting-User: root In-reply-to: shettich@elliot.ics.uci.edu's message of 20 Dec 1995 01:48:32 -0800 In article <4b8m5g$la6@elliot.ics.uci.edu> shettich@elliot.ics.uci.edu (Seth Hettich) writes: In article <4b5t4s$9qv@kelewan.dandelion.com>, Leonard N. Zubkoff <lnz@dandelion.com> wrote: >It's a CD-ROM changer. That means it has a single reader and a mechanism >to automatically switch between the CD-ROMs, transparently to the host >except for the latency involved. Switching from one CD-ROM to another >takes a few seconds, so it will certainly sound like thrashing if you >continually send commands that force the changer mechanism to operate. All >the CD-ROMs are logically available at the same time, but not physically. So can you have 2 users both reading from 2 different CD's, slowly, or will you just get a bunch or errors? basically, would I need to set something up to ensure that 2 CD's won't be read from at the same time? I'm afraid someone familiar with how FreeBSD handles this will have to answer this one. Whether you'll get errors/timeouts or not depends on the kernel, I expect. With a long enough timeout, you can certainly have two different users reading two different CDs slowly. I believe the Linux timeout for SCSI CD-ROMs was increased to 15 seconds to accommodate these changer devices. Leonard