In the aftermath of the previous post, I ended up monitoring the progress of several huge pvmove and md RAID1 resync operations. Running "vmstat 1" however only shows pvmove block I/O activity, but not md RAID1 resyncing. Fortunately, "dstat -d" shows the reads and writes of both pvmove and md RAID1 resync. ("-d" is automatically included in "dstat -a" by the way.) N.B. This only affects block I/O measurements, you'll still see the impact on interrupts and CPU statistics in vmstat.