Re: Where to put what on scsi?

[Ken Hansen <khansen njcc com>]

At 09:34 AM 12/29/98 -0600, you wrote:
>Hello all and Happy New Year,

And to you too!

>I'm new to SCSI.
>But I've read up on it a great deal.

That's good...

>My adapter manual says it's at id7
>by default.  And that the ids are to
>regulate who gets buss access first.

Uh, OK - I was under the impression that the IDs are to "distinguish"
devices from each other, give them a unique ID for commands, etc...

>So that makes me think that putting
>my main disk drive at id6 would be
>a good idea.  But then I got to thinking
>what about my CD drive?  If it is lower
>down the chain and I'm loading programs
>from the CD to the main drive wouldn't that
>slow down the transfer?

No. The SCSI adapter will not give any device improved speed/performance
based solely on it's ID number - the speed of access will be determined by
the capabilities of the SCSI adapter and the SCSI device it is accessing.

>What is a good configuration for drives on
>a scsi chain?

Well, I would suggest something along the following lines, but it really
is whatever you want it to be:

SCSI ID	Device type
-------	-----------------------
   0		Hard drive (Boot device)
   1		Hard drive (2nd drive)
   2		Hard drive (3rd drive)
   3		Hard drive (4th drive)
   4		CD-ROM drive
   5		Removeable SCSI drive (tape, ZIP, Jaz, etc.)
   6		Removeable SCSI drive (tape, ZIP, Jaz, etc.)

Note: When adding hard drives, use SCSI ID#0 first, then 2, 3, then
4 - this is because Linux will refer to the first device it finds as
sda, the second as sdb, etc. and if you start with a drive at ID 4,
when you add a drive with a lower SCSI ID, say 2, IT will become sda
and the drive that you were booting from will become sdb - you will
then have to re-configure the OS to boot and mount partitions from the
sdb drive instead of the sda drive.

Also note: I have placed the removeable drives at ID 5 and 6 because I
suspect/remember that the Iomega devices have limited ID numbe r selections.

Good luck, 

Ken
khansen@njcc.com