qemu-img convert -f raw -O raw /dev/yourvg/yourlv lv1.raw
and if you do
dd if=/dev/yourvg/yourlv of=lv2.raw
?
If not, then the compression if you're using it, or simply memory pressure appears to be the cause, so beside ionice you may want to try to simply use 'nice'
Also, please let us know if using a cgroup works for you (and, if not, please provide all the settings you used).
I've tried again to reproduce this to no avail.
Do you get different behavior if you do
qemu-img convert -f raw -O raw /dev/yourvg/yourlv lv1.raw
and if you do
dd if=/dev/ yourvg/ yourlv of=lv2.raw
?
If not, then the compression if you're using it, or simply memory pressure appears to be the cause, so beside ionice you may want to try to simply use 'nice'
Also, please let us know if using a cgroup works for you (and, if not, please provide all the settings you used).