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Re: [dm-devel] recent bug in dmsetup status of mirror



Douglas McClendon wrote:


Unfortunately, it appears that between the stock F7 kernel -
2.6.21-1.3194.fc7, and the updated F7 kernel 2.6.22.1-41.fc7, the
dmsetup status results on a mirror have regressed.  The userspace tools
are the same in both cases - device-mapper-1.02.17-7.fc7

With the 2.6.21 kernel, after creating a mirror, dmsetup status shows
the mirroring progress, e.g. [1234/56789].  With the 2.6.22 kernel, it
does not.  I don't have the exact output handy to cut and paste, if need
be I can do that, or file a bug.

just noticed it is fixed as of 2.6.22.4-65.fc7

I'm still curious whether write-throttling a mirror is possible. Anybody have any ideas? Can the dm thread be ionice-d? Can the destination device be throttled at the block layer independent of dm? Can the table just be reloaded rapidly, increasing the device size incrementally? It sure does seem to make the system unusable. I.e. when running the following test, it took 10 seconds to open another tab in a gnome-terminal, and then 30+ seconds to launch gedit. (core duo laptop with 1G ram, and reasonably modern sata drive).

#!/bin/bash
dd if=/dev/zero of=./test10ga bs=1k count=1 seek=$(( 1024 * 1024 * 10))
dd if=/dev/zero of=./test10gb bs=1k count=1 seek=$(( 1024 * 1024 * 10))
loa=$( losetup -f )
losetup ${loa} ./test10ga
lob=$( losetup -f )
losetup ${lob} ./test10gb
echo "0 $( blockdev --getsize ${loa} ) mirror core 2 32 sync 2 ${loa} 0 ${lob} 0" | dmsetup create testmir
echo "testmir created"
dmsetup status testmir


thanks,

-dmc


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