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Re: [linux-lvm] LVM2 seems to chop performance by 33%



Thanks

I'd tried that, but no real change. I started 1t 128k and also tried 64k, 256k :) (oh, and 1k)

dd if=/dev/video_vg/video_lv of=/dev/null bs=4k count=256k
262144+0 records in
262144+0 records out
1073741824 bytes transferred in 24.130318 seconds (44497624 bytes/sec)

dd if=/dev/md0 of=/dev/null bs=4k count=256k
262144+0 records in
262144+0 records out
1073741824 bytes transferred in 15.404947 seconds (69701105 bytes/sec)

David

PS wait 'til you see what I'm getting through Rieserfs on top of it!
<sigh>
cu:/huge/editing/tmp# time dd if=dummy.deleteme of=/dev/null bs=4k count=256k
262144+0 records in
262144+0 records out
1073741824 bytes transferred in 31.627904 seconds (33949193 bytes/sec)
so throughput down by a factor of 2...
but 1 step at a time....


Stuart Harper wrote:

While doing backups of my LVM2 drive, I've found that setting the DD block size to 4096 greatly improved my performance. Formerly, DDs on my 240G LVM were taking 23hrs to complete with a block size of 512 or 1024. The same volume now takes less than 2 hours with a block size of 4096. Large numbers did not seem to increase DD speed.

On Thursday 10 June 2004 10:25 am, David Greaves wrote:


65Mb/s on the raid5 device
44Mb/s on the lv

Is this expected?

Kernel 2.6.6

representative dd's:

cu:/huge/editing/tmp# time dd if=/dev/video_vg/video_lv of=/dev/null
bs=1024k count=4k
David


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