Hello,

It's been a while since I've done AIX..., but I'm planning
a new TSM on AIX disk-only backup solution.

I'm planning to make an AIX volume group out of 40 luns of 1 TB.
I'm planning to create one big file system on here.
The purpose for this is to use this as a device class FILE for a TSM disk-only backup solution.

My question is,
would it make any difference, performance-wise, if I split up this capacity over multiple file systems, or even multiple VG's ?

right now this is the plan:
---------------------------------
-> one filesystem on there /FILECLASS/ -> 40 TB
(all backup data will be written to the same file system and VG)

would this be better?:
----------------------------
-> two filesystems on here: /FILECLASS1/ -> 20 TB
/FILECLASS2/ -> 20 TB
(when you specify multiple directories for a device class file in TSM, it spreads its volumes in
a balanced way over the directories that you specify,
so in this case the backups would be landing on 2 different filesystems in the same VG)

would this be even better ?:
------------------------------------
-> one FILESYSTEM on here: /FILECLASS1/
-> one FILESYSTEM on here: /FILECLASS2/
(when you specify multiple directories for a device class file in TSM, it spreads it volumes in
a balanced way over the directories that you specify,
so in this case the backups would be landing on 2 different VG's)

would this make a difference for performance or might I just as well put everything on one file system in one VG ?

Also is there some kind of optimal lun size for this (from an AIX OS perspective) ?


some extra info:

(without DIO since the TSM device class FILE works in a sequential way).

(EMC Ax4 with 2TB SATA2 disks)

any hints/thoughts would be appreciated