Comment 7 for bug 120792

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.