Some comments about performance: - reading works well with big and small block sizes - writing with big block size works ok - the problem arise when writing with small block size
---------- Reading works ok with small and large block size: reading blocks of 1KiB from sda2 # /usr/bin/time dd if=/dev/sda2 of=/dev/null bs=1024 count=$(( 1024*32 )) 32768+0 records in 32768+0 records out 33554432 bytes (34 MB) copied, 0.48956 s, 68.5 MB/s 0.00user 0.07system 0:00.49elapsed 14%CPU (0avgtext+0avgdata 3552maxresident)k 66016inputs+0outputs (0major+268minor)pagefaults 0swaps # /usr/bin/time dd if=/dev/sda2 of=/dev/null bs=1024 count=$(( 1024*1024 )) 1048576+0 records in 1048576+0 records out 1073741824 bytes (1.1 GB) copied, 8.74106 s, 123 MB/s 0.08user 2.23system 0:08.74elapsed 26%CPU (0avgtext+0avgdata 3536maxresident)k 2097632inputs+0outputs (0major+268minor)pagefaults 0swaps reading blocks of 1MiB from sdb2 (to ensure that nothing is cached) # /usr/bin/time dd if=/dev/sdb2 of=/dev/null bs=$((1024*1024)) count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 8.76866 s, 122 MB/s 0.00user 1.82system 0:08.77elapsed 20%CPU (0avgtext+0avgdata 7616maxresident)k 2097408inputs+0outputs (0major+522minor)pagefaults 0swaps Now, writing with blocks of 16MiB works ok (64.5 MB/s!!!) # /usr/bin/time dd if=/dev/zero of=/mnt/rsync/zeros bs=$((1024*1024*16)) count=128 oflag=dsync 128+0 records in 128+0 records out 2147483648 bytes (2.1 GB) copied, 33.2825 s, 64.5 MB/s 0.00user 6.69system 0:33.37elapsed 20%CPU (0avgtext+0avgdata 69072maxresident)k 1464inputs+4195328outputs (0major+4363minor)pagefaults 0swaps With 1MiB the performance is bad (12.1 MB/s) # /usr/bin/time dd if=/dev/zero of=/mnt/rsync/zeros bs=$((1024*1024)) count=256 oflag=dsync 256+0 records in 256+0 records out 268435456 bytes (268 MB) copied, 22.1709 s, 12.1 MB/s 0.00user 0.97system 0:22.17elapsed 4%CPU (0avgtext+0avgdata 7616maxresident)k 40inputs+524288outputs (1major+521minor)pagefaults 0swaps With 1KiB I got.. 33.3 kB/s!!! (I pressed Ctrl+C after some time) # /usr/bin/time dd if=/dev/zero of=/mnt/rsync/zeros bs=1024 count=$(( 1024*32 )) oflag=dsync (pressed Ctrl+C) ^C9069+0 records in 9069+0 records out 9286656 bytes (9.3 MB) copied, 279.276 s, 33.3 kB/s Command terminated by signal 2 0.00user 1.30system 4:39.90elapsed 0%CPU (0avgtext+0avgdata 3504maxresident)k 0inputs+72552outputs (0major+265minor)pagefaults 0swaps -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/893450 Title: libvirt fails to start correctly because LVM is not ready To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/893450/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
