ADSM-L

Re: Using FILE instead of DISK devclass to avoid disk under-utilization

2006-10-26 09:31:02
Subject: Re: Using FILE instead of DISK devclass to avoid disk under-utilization
From: goc <goran.k AT VIP DOT HR>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 26 Oct 2006 15:30:29 +0200
we are using RAID5 in last 6 years as diskpools with no problems whatsoever
we used SSA, now we are using SATA on DS4100

goran

----- Original Message -----
From: "Mark Stapleton" <mark.s AT EVOLVINGSOL DOT COM>
To: <ADSM-L AT VM.MARIST DOT EDU>
Sent: Thursday, October 26, 2006 3:22 PM
Subject: Re: Using FILE instead of DISK devclass to avoid disk
under-utilization


From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Bos, Karel
For normal backup data I like to use JBOD config. No read protection at
all and maximum usable GB per disk. In order to minimize the number of
storage pools needed, ITSM 5.3 has the collecation by group option.

There's a certain amount of sense there. What is the purpose of fault
tolerance in a TSM disk storage pool? At the end of a process cycle, all
customer data exists in at least three or four places:

1. on the client machine
2. in the disk storage pool (if you cache it)
3. on primary (onsite) tape
4. on copy (offsite) tape

Is having fault tolerance for the disk pool really that necessary? Is
yet a fourth (or fifth) level of redundancy worth it?

I rarely find it so. Using JBOD for the disk pool gives you maximum
utilization of disk space and eliminates the issues with RAID
maintenance (either at OS level or the hardware level). I have had
customers who have RAIDed disk catastrophes, and, believe me, running
AUDIT VOL on dozens of disk volumes to clean up the mess afterward is a
royal pain in the butt.

I just never found it all that important.

--
Mark Stapleton (mark.s AT evolvingsol DOT com)
Senior TSM consultant