SUMMARY: Phantom scsi disks in sar output

From: John Horne (J.Horne@plymouth.ac.uk)
Date: Wed Aug 16 2000 - 11:08:48 CDT


Many thanks to all those who replied:

Jonathan Loh <Jonathan.Loh@brodia.com>
Ric Anderson <ric@Opus1.COM>
Jonathon W. Ross <jonathon@isa.net.au>
Joel.Lee@eConnections.com
Changa Anderson <canderson@sitesmith.com>

In answer to the question, I opted for the suggested 'iostat -E' command.

This told me that the device(s) were the CDROM drives. I'll now have to
fiddle with the script we have to get around these. In that respect using
the '-E' option gives me more info about the device; an alternative
suggestion was using the '-en' options - this worked but didn't 'say' that
it was a cdrom device. Instead it said what controller, target etc 'sd30'
and 'sd17' corresponded to. Still, useful to know about these options :-)

As a side issue, I also noticed that on the older systems the CDROM drive has
a target number of 6, but on the newer ones (our Ultra 10's) it defaults to
target number 2. Any reason for this or is it another quirk coming from the
fact that they are PCI based systems?

Thanks again,

John.

The original question was:

On 14-Aug-00 at 10:53:30 John Horne wrote:
> For my manager I produce some monthly stats regarding the performance (?)
> of some of the Sun systems we have here. This is done using sar, and then
> producing a graph of the system, user and disk activity with gnuplot. It's
> nothing fancy but it keeps him happy, and it can show trends in system
> usage.
>
> The question is that we have some Ultra 10 systems, with 9GB internal ide
> disks. They have a scsi card installed but they all seem to report that a
> scsi disk is attached. Eg. this system has a controller but no scsi disks;
> format shows:
>
> AVAILABLE DISK SELECTIONS:
> 0. c0t0d0 <ST39140A cyl 17660 alt 2 hd 16 sec 63>
> /pci@1f,0/pci@1,1/ide@3/dad@0,0
>
> but sar shows:
>
> Average dad0 6 0.3 8 124 25.5 10.7
> dad0,a 6 0.3 8 123 26.2 10.6
> dad0,b 0 0.0 0 0 0.0 26.2
> dad0,c 0 0.0 0 0 0.0 0.0
> dad0,d 0 0.0 0 1 1.6 13.1
> fd0 0 0.0 0 0 0.0 0.0
> nfs1 0 0.0 0 0 0.0 0.0
> sd30 0 0.0 0 0 0.0 0.0
> st4 0 0.0 0 0 0.0 0.0
>
> The software (in-house perl script) used to produce the stats picks up the
> 'sd30' disk, yet it doesn't exist.
>
> Another system has a scsi controller and 2 scsi disks, yet it shows:
>
> [output snipped]
>
> sd1 1 0.0 1 7 0.0 21.1
> sd2 1 0.0 1 7 0.0 17.3
> sd17 0 0.0 0 0 0.0 0.0
> st4 0 0.0 0 0 0.0 0.0
>
> There is no 'sd17'.
>
> Can anyone explain this to me, and have any idea how these 'phantom' disks
> can be 'removed' so that sar doesn't see them?
>

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John Horne, University of Plymouth, UK Tel: +44 (0)1752 233914
E-mail: jhorne@plymouth.ac.uk
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