Date: Fri, 13 Aug 1999 22:09:50 -0500 From: Karl Denninger <karl@Denninger.Net> To: David Kelly <dkelly@hiwaay.net> Cc: Randy Bush <randy@psg.com>, FreeBSD SCSI <freebsd-scsi@FreeBSD.ORG> Subject: Re: dump to dlt gets write error Message-ID: <19990813220950.A57905@Denninger.Net> In-Reply-To: <199908140233.VAA13520@nospam.hiwaay.net>; from David Kelly on Fri, Aug 13, 1999 at 09:33:53PM -0500 References: <karl@Denninger.Net> <199908140233.VAA13520@nospam.hiwaay.net>
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On Fri, Aug 13, 1999 at 09:33:53PM -0500, David Kelly wrote: > Karl Denninger writes: > > I've seen this kind of stupidity before and you're not going to like the > > problem or solution. > > > > Put the DLT on a different SCSI bus (different host adapter) from the disks. > > > > Specifically, separate the fast/wide and narrow SCSI devices. > > > > I've seen both DLTs and other "non-wide" devices have kittens with disks > > running fast/wide on the same SCSI bus. It usually manifests itself as > > an I/O error on the narrow device - which is exactly what you're getting. > > > > My guess is that the hardware on the narrow (and not-so-fast) device gets > > mightily confused by the shorter signal times (even though they're not > > aimed at that target) and randomly "freaks out" enough to botch an > > operation. > > I'd go a bit in the other direction and ask, "How is the transition > between narrow and wide being handled?" Specifically people tend to > purchase "narrow to wide" SCSI cables and simply plug things up with > narrow devices at the tail end of the SCSI bus. Narrow terminator on > the far end, wide terminator on the SCSI card. Nothing in the middle > terminating the high bits of the wide bus. There are special > terminators made just for that purpose. Correct. There are also guidelines on this in general related to the adapter. I'm assuming they are being followed. > You are supposed to be safe if the internal narrow devices are connected > to the 2940UW on the narrow connector, and the wide devices are > connected the same, as long as you don't put a Tee in your SCSI bus by > adding an external device. Just because the 2940UW has 3 connectors > doesn't mean you can use all of them at once. Correct, but not necessarily the issue at hand. > An old used narrow Adaptec 2940, or Symbios '810, or a new Adaptec > 2930, might be a very good solution for the tape and CDROM. Yep. -- -- Karl Denninger (karl@denninger.net) Web: childrens-justice.org Tired of the broken divorce system in the United States and what it's doing to our kids? SIGN the online petition for equal parental - and children's - rights at the above URL. Make a difference in a kid's life today. Real-time chat now available from the above web page To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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