Subject: Re: /dev/[r]sd[5,6]* devices by default ?
To: None <firstname.lastname@example.org>
From: David Laight <David.Laight@btinternet.com>
Date: 01/09/2002 20:00:04
> ...getting back to the original point ( sorry >:} ), traditionally on most
> _supported_ sparc/sparc64 SCSI interfaces (esp, isp?) without getting into
> multiple LUNs, etc., are limited to 7 IDs/targets on the bus, 7 being
> static/taken by the controller/adapter (not changeable that I know) --
> therefore it would make sence to have at least 7 default devices for
> addressable devices (0-6).
Many controllers can have their ID selected, useful if you want 2 host
controllers on the same bus. (comms over scsi! hot failover etc)
And traditionally id 6 is a tape drive...
These days 6 is more likely to be a CDROM.
When we were sizing systems, it was generally not considered worthwhile
(from a throughput point of view) putting more than 1 disk on a scsi
channel. It was much more common to add extra controllers for the
other disks. Certainly you wouldn't consider 7 disks on one 8-bit
scsi channel for any form of server, the scsi data rate is far too slow.