Many many times beaten to dead on this forum. You can find tons of
discussions and valuable information in the archives.
IM(ns)HO the database will feel more comfortable on RAID 1/10 or software
mirrored volumes. RAID 5 will suffer from random writes and the problem
grows with number of disks. 8 disks are a way too much for heavily used
RAID 5 if big memory cache (at least 8 GB in IBM ESS) is not available.

Zlatko Krastev
IT Consultant






Leonard Lauria <leonard AT UKY DOT EDU>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
21.08.2003 15:53
Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        opinions on disk partitioning


I would like to get opinions on disk configurations for a new platform.

I am installing my TSM server on an aix platform, with FASTT700 disk.

The FASTT700 has (28) 73 GB, 15K disks, of which 23 are available for this
application.

I am considering the following 2 setups, but please feel free to make
other
suggestions!

1)  12 drives for the TSM DB, raid 10.  I only need 100 GB, plus room to
grow,
           perhaps double, so this wastes a lot of space, but I get needed
spindles.
       Remaining 11 drives would be Raid 5, and exported as a single LUN
which would
           have 4 logical volumes for:

             570 GB disk pool
             200 GB disk pool
               20 GB disk pool
               13 GB TSM log

2)  8 drives for the TSM DB, raid 5.  I only need 100 GB, plus room to
grow,
           perhaps double, so this is less space, but fewer spindles and
no
mirror.
       Remaining 15 drives would be Raid 5, and exported as a single LUN
which would
           have 4 logical volumes for:

             500 GB disk pool
             500 GB disk pool
               82 GB disk pool
               13 GB TSM log

#2 gives me more spindles for the disk pools, by using only raid5 for the
database partitions.

Another concern is having the disk pools compete with each other on the
same disks.  Would
it be better to have fewer spindles per disk pools, but have disk pools
seperate from each other,
or all the disk pools spread over the same larger number of spindles?

Also, I have had a lot of conflicting information regarding TSM doing
mirrors of the DB and LOG
versus letting the FASTT hardware do raid protection.  It seems the
hardware implementation would
be faster, and just as safe, as letting TSM do mirrors...not to mention
allowing me to spread things
out a bit more.

Any opinions on my options?

Thanks!

leonard