用dd簡單測Linux的io

read:

# time dd if=/dev/sda of=/dev/zero bs=8k count=1000000

1000000+0 records in

1000000+0 records out

8192000000 bytes (8.2 GB) copied, 73.0053 s, 112 MB/s

real    1m13.025s

user    0m0.230s

sys     0m7.700s

write:

#time dd if=/dev/zero of=/tmp/fake.file bs=8k count=1000000

1000000+0 records in

1000000+0 records out

8192000000 bytes (8.2 GB) copied, 81.6353 s, 100 MB/s

real    1m21.758s

user    0m0.160s

sys     0m8.440s

read and write:

#time dd if=/tmp/fake.file of=/tmp/fake.file.out bs=8k count=1000000

1000000+0 records in

1000000+0 records out

8192000000 bytes (8.2 GB) copied, 207.892 s, 39.4 MB/s

real    3m27.960s

user    0m0.320s

sys     0m17.310s

檢查Linux Block size

# dumpe2fs /dev/sdb1 | grep -i 'Block size'

測試 Ram Disk的速度.(註:/tmp採用Ram Disk)

# time dd if=/dev/zero of=/tmp/fake.file bs=8k count=400000

400000+0 records in

400000+0 records out

3276800000 bytes (3.3 GB) copied, 1.33236 s, 2.5 GB/s