Date: Tue, 9 Jul 2002 16:10:15 -0600 From: "Kenneth D. Merry" <ken@kdm.org> To: David Gilbert <dgilbert@velocet.ca> Cc: Keith Pitcher <kpitcher@locallink.net>, freebsd-hackers@FreeBSD.ORG Subject: Re: [hackers] Multi CDR burn Message-ID: <20020709161015.A75408@panzer.kdm.org> In-Reply-To: <15659.17952.903580.570415@canoe.velocet.net>; from dgilbert@velocet.ca on Tue, Jul 09, 2002 at 04:22:56PM -0400 References: <20020708220105.GA32341@stone.locallink.net> <15658.50186.945164.162061@canoe.velocet.net> <20020709191404.GA97352@stone.locallink.net> <15659.17952.903580.570415@canoe.velocet.net>
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On Tue, Jul 09, 2002 at 16:22:56 -0400, David Gilbert wrote: > >>>>> "Keith" == Keith Pitcher <kpitcher@locallink.net> writes: > > Keith> Given the hardware, is there a way to burn 8 CDs at one time, > Keith> or is there some mirroring code that is well written enough to > Keith> facilitate it? > > I wouldn't expect mirroring code to be of help here since FreeBSD's > vinum and ccd expect disk formats (not iso_9660) and also expect > regular read/write disks, not CDR (which require special treatment > anyways). > > I also didn't know that there was a write-to-many SCSI command? > Someone can confirm or deny this? There is no such thing. > A narrow SCSI2 bus is 20Mhz * 8 bit or 20 Megabytes per second. A 1x > CDROM is 20 kilobytes per second (roughly, I looked it up and several > sources said 150 kilobits per second) ... so your single scsi bus > should handle 1000 1x CDROMS or 8 125x CDROMS. Simply put, your SCSI > channel (even it it's only 10Mhz is way more then enough). > > Next, let the OS do the work. You'll likely find that you can set the > buffers to almost zero (I think the default is one meg). The code > will be shared, the data will only be read once and you just might > find that it works. UNIX is there to make these simple things work > for you. > > I'll go out on a limb and speculate that there isn't a write-to-many > command as you suggest. My understanding of SCSI is that each command > addresses one target... and that part of the format is hard-coded. You're correct. With SCSI, one initiator talks to one target, so you can't talk to multiple targets at one time. As long as the drives support disconnection, you should be able to burn multiple CDs at once over one bus. Ken -- Kenneth Merry ken@kdm.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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