Just recently I had 2 clients where their TSM server crashed (Windows..go 
figure!) and wouldn't start back up again with log
corruption errors. I managed to get both of them back up by renaming the 
primary log volume(s) and starting TSM. Came right
up...complained about not having the primary volume, but moved to the logcopy 
volume which wasn't corrupted due to the system crash.

Like Allen...I'm sticking with the mirrors!


Bill Boyer
"Some days you're the bug, some days you're the windshield" - ??

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Allen S. Rout
Sent: Saturday, January 21, 2006 10:19 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: DB & LOG Volume layout - new

>> On Fri, 20 Jan 2006 14:02:28 -0500, David Longo <David.Longo AT HEALTH-FIRST 
>> DOT ORG> said:


> I've just done a reconfig of my DB and LOG volumes that flies in the
> face of conventional wisdom - but it works!

[...]

I think that most TSM admins tend to prefer as many ways to keep their pants up 
as can be arranged.  I've mused in the past that, if
IBM allowed 4 copies of a volume, than three would very quickly become de 
rigeur for standard running.  (you -need- the unallocated
copy if you're going to migrate to new disk tech)

For a long time I used as many spindles as I could, to free database
work of contention.   With disk tech such as you are using now, and
huge caches reliably inserted between you and the disk, the strength of that 
need has dropped precipitously.

RAID on the back-end ameliorates many (but as has been pointed out, clearly not 
all) of the risks which the TSM-level mirror was
intended to address.  As a result, your 2:1 cost penalty for mirror disk 
allocation (mumble RAID overhead, mumble hot spare
overhead) is being deployed to chase a smaller and smaller risk.  It is 
entirely rational to conclude that, in your environment it
is "too much" cost for "not enough" coverage.

But I would very strongly suggest that you put numbers by that cost, and try to 
estimate the risk, too.  Ever do dimensional
analysis in physics or chemistry?

Re-express 5 SATA disks in hours-of-service-down. :) I'm keeping the mirrors.


- Allen S. Rout