From: Mike Broderick (broderic@MIT.EDU)
Date: Fri Apr 11 2003 - 15:58:09 EDT
Our DLT7000 tape drives (DLT IV tapes, attached to several systems via a
SAN and in a StorageTek ATL) recently started filling up at half their
[h/w] compressed capacity recently. (Netbackup kicks them out just
before about 35GB.) It was first noticed on one tape and now all tapes
are only taking 35GB (We specify the tapeN_d1 device). We see the same
problem (out of tape) w/ a simple manual tar dump to tape of about 40GB.
It seems like h/w compression is no longer happening.
We manually loaded back on of the tapes and the compression light did
not come on. We thought we saw a strong correlation to upgrading to pk4
from pk3 but alas the one system still at pk3 also does not compress
anymore either. We also backed down the drive f/w revs recently (to a
version we use in another environment that compresses fine). We are
checking w/ StorageTek for possible known issues with the firmware rev
(but unlikely since it works for us elsewhere).
I've seen hints to a bit in the minor device ID that indicates compression.
What bit is this? Is there some way (e.g., mt status? ddr_config?) to
query the device/drive from 5.1a and see if it is set for compression.
I've looked at output from these two commands but am not sure what I'm
looking for?
_Mike
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