Date: Tue, 21 Dec 1999 12:04:00 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Peter Jeremy <peter.jeremy@alcatel.com.au> Cc: Greg Lehey <grog@lemis.com>, FreeBSD current users <FreeBSD-current@FreeBSD.ORG> Subject: Re: Recent current hangs frequently for 1 to 2 seconds. Message-ID: <199912212004.MAA80595@apollo.backplane.com> References: <19991219143759.C465@freebie.lemis.com> <199912190416.UAA01125@apollo.backplane.com> <19991221095213.L440@freebie.lemis.com> <199912210019.QAA62510@apollo.backplane.com> <19991221110148.N440@freebie.lemis.com> <199912210108.RAA62736@apollo.backplane.com> <99Dec21.123129est.40326@border.alcanet.com.au>
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:On 1999-Dec-21 12:08:27 +1100, Matthew Dillon <dillon@apollo.backplane.com> wrote:
:> Tape drives may:
:> * Not support disconnection ...
:> * Implement a crappy SCSI command stack ...
:> * Not properly terminate the SCSI bus ...
:> * Introduce too much noise onto the SCSI bus due to bad design.
:
:Do modern drives still support these various `features'? I know
:there used to be problems, but I thought Greg was using a (presumably
:fairly recent) DLT drive. Given the normal data rates associated with
:DLT drives, I would have thought they would behave fairly well.
:
:BTW, since Greg mentioned he was thinking of using an AHA-1542B -
:I've found that mine won't work in sync mode. Whenever I tried to
:read or write, it would just timeout, until I disabled SYNC. (And
:if I increased the sync speed beyond 5MHz, the kernel would usually
:panic).
:
:Peter
They are supposed to support disconnection, and most do. But tape
drives tend to have buggy firmware - for example, the 20G Exabyte
drives can crash a SCSI bus if you use too small a block size. It
just isn't worth mixing them with your disks.
-Matt
Matthew Dillon
<dillon@backplane.com>
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