On Fri, Apr 23, 2010 at 06:26:20PM +0400, Michael Tokarev wrote:
This is most likely due to read-modify-write cycle which is present on
lvm-on-raid[456] if the number of data drives is not a power of two.
LVM requires the block size to be a power of two, so if you can't fit
some number of LVM blocks on whole raid stripe size your write speed
is expected to be ~3 times worse...
uh?
PE size != block size.
PE size is not used for io, it is only used for laying out data.
It will influence data alignment, but i believe the issue may be
bypassed if we make PE size == chunk_size and do all creation/extension
of LV in multiple of data_disks, the resulting device-mapper tables
should be aligned.
L.
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