[HPDD-discuss] Draining an OST

We are running lustre 2.1.6 on SL6.4 systems. Most OST date back to lustre 1.8.4 under SL5.x. I now find it necessary to drain and reformat the underlying RAID volume of one of these OST. I have done this several times in the past, under lustre 1.8.4, and was highly satisfied with the outcome. However, I find this somewhat more problematic under 2.1.6 now. Basically, in the two examples so far, corrupted files have resulted. I have used lfs_migrate to first drain, then refill the OST after it is reformatted. It is much faster now than under 1.8.4, which is nice. Do I have to do this on an idle file system though to avoid the corruption? The two previous examples were still live, so it was possible that the corrupted files were being accessed at the time? Could this have been the cause of the problems? What am I missing in doing this now under 2.1.6? Thanks in advance, bob