same crummy performance on quantal, so the bad performance may be unrelated:
vishvananda@nebstack006:~$ sudo dd if=/dev/zero of=/dev/mapper/clean1 bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 15.2082 s, 70.6 MB/s
vishvananda@nebstack006:~$ time sudo dd if=/dev/zero of=/dev/mapper/clean1 bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 8.00752 s, 134 MB/s
same crummy performance on quantal, so the bad performance may be unrelated:
vishvananda@ nebstack006: ~$ sudo dd if=/dev/zero of=/dev/ mapper/ clean1 bs=1M count=1024 nebstack006: ~$ time sudo dd if=/dev/zero of=/dev/ mapper/ clean1 bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 15.2082 s, 70.6 MB/s
vishvananda@
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 8.00752 s, 134 MB/s
real 0m8.017s
user 0m0.008s
sys 0m1.116s