Seams last comment has double c/p, making it hard to read. Here goes another result (for some reason, I get a bunch of "DD Finished", I didn't want to cut as do not know if its relevant for test - probably not): Using current dir to do IO tests First Test: How much gets to run the CPU intensive task? We have Burning CPU with 7139 min:0.005ms|avg:0.015-0.031ms|mid:0.000ms|max:0.000ms|duration:22.600s We have Burning CPU with 8947 min:0.004ms|avg:0.014-0.031ms|mid:0.000ms|max:0.000ms|duration:22.342s Second Test: Does the process queue get blocked because high IO? Starting We have High IO PID 10772 We have Burning CPU with 10773 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 14.7651 s, 14.2 MB/s 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 16.8547 s, 12.4 MB/s DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 18.5809 s, 11.3 MB/s DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 19.6679 s, 10.7 MB/s DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 20.7152 s, 10.1 MB/s DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished 200+0 records in 200+0 records out 209715200 bytes (210 MB) copied, 22.0414 s, 9.5 MB/s DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished DD Finished min:0.004ms|avg:0.018-0.033ms|mid:0.000ms|max:0.000ms|duration:24.033s DD Finished IO Finished before than processing --- Finish --- Kernel tested: 2.6.27-13-generic x86_64 This is ext3.