Disk IO issues
ricky at fedoraproject.org
Wed Dec 31 22:26:27 UTC 2008
On 2008-12-31 10:49:56 PM, Xavier Lamien wrote:
> Could you perform an hdparm -tT on that disk ?
Timing cached reads: 2668 MB in 2.00 seconds = 1336.06 MB/sec
Timing buffered disk reads: 1024 MB in 3.01 seconds = 340.69 MB/sec
> Also, output an strace against your cat & dd commands.
> if my memory is good enough, cat use mmap() which is faster than
> read() (which is used by dd)
I just straced dd and cat, and it looks like cat is using a block size
of 4096 bytes while dd is using 512 bytes. I *think* they were both
just using read(). Perhaps dd if=/dev/sde of=/dev/null bs=4096 would be
a better command to compare against.
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