Use of "lvconvert -m 1 --corelog vg00/testdisk" on data that you care
about is a bad idea. This tells LVM to create the log in memory. When a
write occurs, it is written to disk and the log. Should one disk
complete before the other (which is very likely to happen, especially
with non-disk PVs), the only thing ensuring write completion on the
second disk is the log. In this window, should a crash/reboot/power
outage occur, which is likely on a heavy I/O bound server, loss of
mirror synchronization is likely. On the next boot, when the data mirror
would otherwise be restarted and completed on the second (or more) disk,
it is no longer available (was in memory). Since the log is no longer
available, the pending write can not complete. You now have a mirror
which is no longer properly synchronized. This can result in data loss.
Don't do this. Frankly it's not clear to me what value --corelog has
other than testing and debugging.

-- 
lvcreate fails with mirror raid1
https://bugs.launchpad.net/bugs/120792
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