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tar's default block size & shoe-shinning
2006-06-19 04:12:50
Hi all,
Could someone tell me if there are any possibilities
to change the block size tar is using when backuping with amanda?
I'm asking this because we have recently
bought an IBM ULTRIUM-TD3 LTO3 drive here and Amanda reports an average
write rate of only 17MB/s (when the maximum speed should be 40 MB/s uncompressed).
Which most probably means that the drive is shoe-shinning...
I think, tar's default block size of 10k
is the most limiting factor since the constructor recommends a block size
of 64kb and tests with "dd" reported a transfer speed of 33MB/s
with bs=64k and only reports a 25MB/s with bs=10k.
I'm using amanda-2.4.4p1-0.3E (Red Hat ES
3.3).
Best regards,
Cyrille Bollu
=================================
Here are the full results from my "dd"
tests:
bs time
(sec) calculated speed (MB/s)
===================================
64k
95
33,7
32k
100
32
10k
130
24,6
4k
173
18,5
1k
409
7,8
(results from the command "time dd if=/dev/sda2
of=/dev/nst0 bs=<var1> count=<var2>". Where <var2>
is calculated so that <var1>*<var2>=3200MB)
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