Hi all,
Recently, I migrated our TSM server from an RS/6000 H50 to an H80. During this
process, my TSM database changed from 5 - 9.1 GB SSA drives to 3 - 18 GB SSA
drives. (Acutally, 10 - 9.1's and 6 - 18's utilizing TSM mirroring).
In the old config. I had used raw volumes, as recommended by a consultant when
the system first arrived. IBM TSM Support felt there was no discernible
performance difference between raw and jfs filesystems for the TSM DB volumes,
so I opted for jfs on the new config. I can't judge the difference as my
performance has increased by about 40%, but I went from a 4-way H50 to a 4-way
H80, and from 80 MB/s SSA to 160 MB/s SSA. Has anyone tried raw vs. AIX jfs for
TSM DB performance?
The other question I posed to IBM TSM Support was how to configure the 3 -18GB
SSA disks: Three separate filesystems, each with a DB volume file, or one
filesystem striped across all three disks, providing TSM one DB volume. They
were unable to tell me whether TSM would manage the three DB vols in parallel or
serial, but felt that the three vs. one striped was the way to go. Now that I
am done, I see, using iostat, that during a DB backup it is only accessing one
drive of the three at a time, showing me that TSM uses these volumes
sequentially, not in parallel. Would I not get better TSM DB performance with
one logical volume/filesystem striped across all three drives? If not, why? If
so, large or small stripe size?
Thanks,
Joe Goshko
ADC Software Systems
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