On 03/11/2013 11:56 PM, Josh Durgin wrote: >> dd if=/dev/zero of=/bigfile bs=2M & >> >> Serial console gets jerky, VM gets unresponsive. It doesn't crash, but >> it's not 'healthy' either. CPU load isn't very high, it's in the waiting >> state a lot: > > Does this only happen with rbd_cache turned on? If so, it may be the > same cause as http://tracker.ceph.com/issues/3737. Indeed it does only happen with rbd_cache turned on. Without the cache the jerking doesn't happen, but it's slower by a factor of three (well - we knew this before, right): (without rbd-cache): dd if=/dev/zero of=/bigfile bs=2M count=100 209715200 bytes (210 MB) copied, 9.32188 s, 22.5 MB/s (with rbd-cache): dd if=/dev/zero of=/bigfile bs=2M count=100 209715200 bytes (210 MB) copied, 3.12769 s, 67.1 MB/s And yes, we've also seen lost packets on the network on a busy machine with rbd_cache, so this is totally the issue in the bugtracker. Wolfgang _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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