From: Jeffrey_Hummel@albemarle.com
Date: Tue Jun 01 2004 - 12:37:26 EDT
Many thanks are deserved by Alan Rollow, Fred Serino, Denise McKracken, and
Olle Bjorck.
There were no specific changes that caused the slowdown in backup speeds.
The most likely cause in our case was the coincidental use of older tapes
after we upgraded the system combined with some additional OS overhead from
the new version of UNIX.
The tapex command was great because it allowed us to verify that we could
achieve 4MB/sec. to/from the TZ89 tape drives with block sizes from 32k to
64k.
The suggestions to backup to /dev/null were great because it also showed us
that if we were backing up from disk to disk we could move a 2GB file in
one minute instead of 4 1/2 minutes by increasing the blocksize from 64k to
16MB. The point of greatly diminished improvements was experienced around
8MB /sec. The configuration for this test was a DS-RZ1FC-VW -> KZPBA-CB ->
KZPBA-CB -> DS-RZ1FC-VW.
Additionally, we loaded the ltt tape library tool and discovered that a
tape drive that had been problematic was showing a firmware version that
was much older than the rest of our tape drives.
Thanks everybody for the suggestions!
Jeffrey Hummel
Albemarle Corporation
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