Re: DDS-3 tapetype ???
2005-06-18 14:13:58
OK, here is my solution that allows full tape length for my backups.
Notice that I am using amtapetype only as an effective way to illustrate
both my problem and the solution.
This demonstrates using the OS and mt to turn tape drive hardware
compression ON:
* Michael D Schleif <mds AT helices DOT org> [2005:06:17:10:04:59-0500] scribed:
<snip />
> # sudo /bin/mt -f /dev/nst0 compression 1
>
> # sudo /bin/mt -f /dev/nst0 defcompression 1
>
> # sudo -u backup amtapetype -c -f /dev/nst0 -o
> Writing 1024 Mbyte compresseable data: 384 sec
> Writing 1024 Mbyte uncompresseable data: 1318 sec
> WARNING: Tape drive has hardware compression enabled
> Estimated time to write 2 * 1024 Mbyte: 2636 sec = 0 h 43 min
This demonstrates using the OS and mt to turn tape drive hardware
compression OFF:
# sudo /bin/mt -f /dev/nst0 compression 0
# sudo /bin/mt -f /dev/nst0 defcompression -1
* Michael D Schleif <mds AT helices DOT org> [2005:06:16:23:59:28-0500] scribed:
<snip />
> # time sudo -u backup amtapetype -e 12g -f /dev/nst0 -o
> Writing 32 Mbyte compresseable data: 37 sec
> Writing 32 Mbyte uncompresseable data: 35 sec
> Estimated time to write 2 * 12288 Mbyte: 26880 sec = 7 h 28 min
> wrote 298832 32Kb blocks in 76 files in 10632 seconds (short write)
> wrote 310628 32Kb blocks in 158 files in 10840 seconds (short write)
> define tapetype unknown-tapetype {
> comment "just produced by tapetype prog (hardware compression off)"
> length 9522 mbytes
> filemark 0 kbytes
> speed 908 kps
> }
>
> real 364m39.451s
> user 0m2.724s
> sys 0m28.719s
Next, the Compaq/Sony SDT-9000 a physical jumper labeled `disable dc'.
To this point, this jumper was OPEN. Now I CLOSED this jumper.
Interestingly, now when I used the OS and mt to set both compression and
defcompression to 1, the following test _never_ returns an initial
estimate:
# sudo -u backup amtapetype -c -f /dev/nst0 -o
Finally, with the jumper CLOSED, compression 0 and defcompression -1, I
get the following:
# time sudo -u backup amtapetype -e 12g -f /dev/nst0 -o
Writing 128 Mbyte compresseable data: 114 sec
Writing 128 Mbyte uncompresseable data: 114 sec
Estimated time to write 2 * 12288 Mbyte: 21888 sec = 6 h 4 min
wrote 365676 32Kb blocks in 93 files in 11010 seconds (short write)
wrote 365676 32Kb blocks in 186 files in 10484 seconds (short write)
define tapetype unknown-tapetype {
comment "just produced by tapetype prog (hardware compression off)"
length 11427 mbytes
filemark 0 kbytes
speed 1089 kps
}
real 373m59.100s
user 0m2.907s
sys 0m30.466s
Most importantly, last night's backup used nearly the whole 12 GB of tape!
Thank you, all of you, for your contributions to this challenge.
--
Best Regards,
mds
mds resource
877.596.8237
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Dare to fix things before they break . . .
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Our capacity for understanding is inversely proportional to how much
we think we know. The more I know, the more I know I don't know . . .
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