Linux on PE2950, PV220S and very slow PV124T
haazeloud at gmail.com
Mon Aug 25 03:46:35 CDT 2008
> You should be able to read the tape quickly, if the hardware is good:
> % tar -tbf 128 /dev/st0
> Note that the blocking factor should not matter much for performance, it
> is not really necessary.
> Also, check value of TAR_OPTIONS; if you have compression or other
> things turned on then this may be affecting performance by not blocking
> the data to 128 blocks, for example.
> Another test, which avoids questions of filesystem state, disk
> throughput, etc, is simply to dd to the tape device. This should run
> really fast due to ease of compression:
> % time dd if=/dev/zero of=/dev/nst0 bs=1M count=1000
> a gig should take 10 to 20 seconds.
TAR_OPTIONS is empty.
% date && echo "" && tar -tb 128 -f /dev/st0 > /dev/null && echo "" && date
58 mins !
% dd if=/dev/zero of=/dev/nst0 bs=1M
dd: writing `/dev/nst0': Device or resource busy
1+0 records in
0+0 records out
0 bytes (0 B) copied, 2.43528 seconds, 0.0 kB/s
For tar, i should use tar -b 128 -cvf /dev/st0 et not tar -cvbf 128
/dev/st0 or tcsh make an error... :)
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