I had an HP DDS2 drive, and gradually adjusted tapetype over time to
reduce EOT occurrences. I don't put much stock in the nominal 4 GB
capacity.
Here's what I ended up with. I had a few premature EOT events after
that, but didn't adjust since they seemed to be anomalous.
I don't know if the 100 for filemark is correct. I copied it from
someone else's tapetype. But since this setup always writes ~60
files, the value doesn't matter much, as long as
written-kb + 60*filemark = theoretical-capacity
because I calculate theoretical-capacity from written-kb and a guess
at filemark and then planner undoes this when seeing if things fit.
A script to go over logs (egrep 'INFO taper' log.* | crunch) and plot
green dots for successful finishes and red dots for hitting EOT would
be cool. Then one could eyeball the average actual tape length and
choose a value to give infrequent overruns.
define tapetype HP-DDS2 {
comment "C1599A with DDS2-120m tape"
# length 3800 mbytes
# length 3675 mbytes (* 3675 1024)
# 2000-03-15 error after:
# (/ (+ 3630752 (* 58 100)) 1024.0) =3551
# 2000-04-05 error after
# (/ (+ 3619776 (* 61 100)) 1024.0) =3540 (tape 025, leave at 3550)
# 2000-08-09 error after
# (/ (+ 3590784 (* 58 100)) 1024.0) =3512 (tape 020, leave at 3550)
length 3550 mbytes
filemark 100 kbytes
speed 450 kbytes
}
Here are a bunch of examples of hitting EOT, sorted by amount written.
(Note that one is very short; this was because FOO_900 was a DDS1 tape.)
INFO taper tape FOO_900 kb 1968192 fm 65 writing file: No space left on device
INFO taper tape FOO_026 kb 2661856 fm 57 writing file: No space left on device
INFO taper tape FOO_006 kb 3333184 fm 26 writing file: No space left on device
INFO taper tape FOO_008 kb 3334176 fm 56 writing file: No space left on device
INFO taper tape FOO_026 kb 3553888 fm 61 writing file: No space left on device
INFO taper tape FOO_020 kb 3590784 fm 58 writing file: No space left on device
INFO taper tape FOO_025 kb 3592352 fm 60 writing file: No space left on device
INFO taper tape FOO_021 kb 3592608 fm 58 writing file: No space left on device
INFO taper tape FOO_021 kb 3593888 fm 10 writing file: No space left on device
INFO taper tape FOO_025 kb 3619776 fm 61 writing file: No space left on device
INFO taper tape FOO_021 kb 3630752 fm 58 writing file: No space left on device
INFO taper tape FOO_020 kb 3637664 fm 57 writing file: No space left on device
INFO taper tape FOO_027 kb 3648928 fm 60 writing file: No space left on device
INFO taper tape FOO_026 kb 3652480 fm 56 writing file: No space left on device
INFO taper tape FOO_027 kb 3658912 fm 60 writing file: No space left on device
INFO taper tape FOO_023 kb 3767072 fm 57 writing file: No space left on device
INFO taper tape FOO_032 kb 3846528 fm 57 writing file: No space left on device
INFO taper tape FOO_033 kb 3866016 fm 52 writing file: No space left on device
INFO taper tape FOO_035 kb 3887392 fm 55 writing file: No space left on device
INFO taper tape FOO_037 kb 3904544 fm 53 writing file: No space left on device
INFO taper tape FOO_031 kb 3931456 fm 51 writing file: No space left on device
I'm not 100% sure if the 'kb' number includes #fm * filemarksize bytes
for filemarks, or if it is just the sum of the sizes. I'm assuming
just the sum. But with disks these days, filemarks are generally
too small to matter much, it seems.
Greg Troxel <gdt AT ir.bbn DOT com>
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