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From: eckert@faui43.informatik.uni-erlangen.de (Toerless Eckert)
Newsgroups: comp.sys.sun,comp.periphs.scsi
Subject: Exabyte and se controller
Keywords: Hardware
Message-ID: <8680@brazos.Rice.edu>
Date: 8 Jun 90 13:15:48 GMT
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X-Sun-Spots-Digest: Volume 9, Issue 207, message 3

Some time ago i asked about a problem with our Sun 3/180 and it's Exabyte.
The machine had an Exabyte and a shoebox connected to its se0 SCSI
controller. When the Exabyte was active, for example rewinding or
searching for a file, the machine would often block.

The problem is, that the se VME-SCSI controller for Sun3 (and possible
also sold for Sun4) does not support the DISCONNECT/RECONNECT abilities of
the SCSI protocol. This caused the scsi driver in the Sun to allocate the
SCSI bus during all transactions, for example the rewinding or searching
for files, which do not need to hold the bus.  The next effect of this
was, that someone accessing the filesystem on the SCSI filesystem could
possible lock the whole filesystem in the kernel during these Exabyte
activites.

So, if you are using a VME Sun with both exabyte (or other slow tape
devices) and a SCSI disk, you are well advised to change your old se
Controller against the newer si controllers, which do support the
DISCONNECT/RECONNECT part of the SCSI protocol. We did this with our board
on maintenance so it didn't cost us a buck.

Toerless Eckert          | /C=de/A=dbp/P=uni-erlangen/OU=informatik/S=eckert
V.4: Noah's ark of Unix  | X.400 ^ Internet> eckert@informatik.uni-erlangen.de