my mongo env:
3shard +3mongos

insert ops/s:800000,but update just to 20% dirty

insert query update delete getmore command dirty used flushes vsize res qrw arw net_in net_out conn set repl time
*0 22368 *0 *0 10 107|0 0.0% 80.1% 0 104G 95.5G 2|0 5|0 16.2m 190m 173 myShard_2 PRI May 20 17:18:19.869
*0 20177 *0 *0 11 106|0 0.0% 80.1% 0 104G 95.5G 0|0 5|0 14.6m 221m 173 myShard_2 PRI May 20 17:18:20.870
*0 15732 *0 *0 4 93|0 0.0% 80.1% 0 104G 95.5G 0|0 1|0 11.4m 132m 173 myShard_2 PRI May 20 17:18:21.875
*0 20317 *0 *0 9 92|0 0.0% 80.1% 0 104G 95.5G 0|0 3|0 14.7m 155m 173 myShard_2 PRI May 20 17:18:22.870
*0 21517 *0 *0 12 118|0 0.0% 80.1% 1 104G 95.5G 0|0 4|0 15.6m 206m 173 myShard_2 PRI May 20 17:18:23.869
*0 9703 *0 *0 9 100|0 0.0% 80.1% 0 104G 95.5G 0|0 3|0 7.05m 177m 173 myShard_2 PRI May 20 17:18:24.871
*0 22103 *0 *0 5 73|0 0.0% 80.0% 0 104G 95.5G 0|0 5|0 15.9m 122m 173 myShard_2 PRI May 20 17:18:25.869
*0 4872 *0 *0 4 39|0 0.0% 80.0% 0 104G 95.5G 0|0 3|0 3.53m 55.2m 173 myShard_2 PRI May 20 17:18:26.868
*0 9187 *0 *0 9 100|0 0.0% 80.0% 0 104G 95.5G 1|0 3|0 6.68m 160m 173 myShard_2 PRI May 20 17:18:27.868
*0 20451 *0 *0 5 92|0 0.0% 80.0% 0 104G 95.5G 0|0 8|0 14.8m 121m 173 myShard_2 PRI May 20 17:18:28.869
insert query update delete getmore command dirty used flushes vsize res qrw arw net_in net_out conn set repl time
*0 19316 *0 *0 5 87|0 0.0% 80.0% 0 104G 95.5G 0|0 3|0 14.0m 154m 169 myShard_2 PRI May 20 17:18:29.869
*0 15054 30045 *0 5 73|0 2.6% 80.7% 0 104G 95.5G 0|1 5|13 13.9m 81.9m 169 myShard_2 PRI May 20 17:18:30.872
*0 13118 60393 *0 6 42|0 4.4% 80.4% 0 104G 95.5G 0|1 7|14 15.2m 114m 168 myShard_2 PRI May 20 17:18:31.871
*0 11762 56620 *0 4 106|0 5.9% 81.5% 0 104G 95.5G 1|0 4|14 13.8m 79.1m 169 myShard_2 PRI May 20 17:18:32.869
*0 10904 39783 *0 5 73|0 6.8% 82.3% 0 104G 95.5G 0|0 5|15 11.5m 111m 166 myShard_2 PRI May 20 17:18:33.871
*0 11204 41323 *0 6 82|0 7.8% 83.1% 0 104G 95.5G 0|0 8|15 12.0m 112m 166 myShard_2 PRI May 20 17:18:34.870
*0 11269 46003 *0 5 66|0 8.9% 83.9% 0 104G 95.6G 2|1 4|15 12.6m 112m 166 myShard_2 PRI May 20 17:18:35.872
*0 11407 36047 *0 6 59|0 9.8% 84.6% 0 104G 95.8G 0|0 8|15 11.5m 112m 165 myShard_2 PRI May 20 17:18:36.870
*0 10735 38157 *0 5 56|0 10.7% 85.3% 0 104G 96.2G 0|0 5|14 11.3m 111m 165 myShard_2 PRI May 20 17:18:37.870
*0 5842 34431 *0 2 43|0 11.4% 85.9% 0 104G 96.6G 0|0 2|16 7.53m 73.1m 165 myShard_2 PRI May 20 17:18:38.869
insert query update delete getmore command dirty used flushes vsize res qrw arw net_in net_out conn set repl time
*0 15050 3824 *0 1 41|0 20.1% 80.0% 0 104G 102G 2|0 6|16 11.2m 48.5m 164 myShard_1 PRI May 20 17:19:05.416
*0 14218 3968 *0 4 48|0 20.1% 80.0% 0 104G 102G 0|0 5|16 10.6m 81.3m 164 myShard_1 PRI May 20 17:19:06.415
*0 15395 3865 *0 4 74|0 20.1% 80.0% 0 104G 102G 0|0 12|16 11.4m 82.6m 159 myShard_1 PRI May 20 17:19:07.415
*0 8436 5760 *0 1 35|0 20.1% 80.0% 0 104G 102G 0|0 3|12 6.52m 41.9m 159 myShard_1 PRI May 20 17:19:08.416
*0 14809 4036 *0 4 44|0 20.1% 80.0% 0 104G 102G 2|0 7|16 11.3m 81.9m 147 myShard_1 PRI May 20 17:19:09.415
*0 7141 5948 *0 1 22|0 20.1% 80.0% 0 104G 102G 0|0 9|16 5.68m 74.2m 132 myShard_1 PRI May 20 17:19:10.416
*0 10626 4264 *0 4 45|0 20.1% 80.0% 0 104G 102G 2|0 4|16 8.01m 44.1m 129 myShard_1 PRI May 20 17:19:11.416
*0 15534 3356 *0 3 35|0 20.1% 80.0% 0 104G 102G 5|0 5|16 11.6m 82.5m 122 myShard_1 PRI May 20 17:19:12.416