On 17/07/2011 13:22, Iustin Pop wrote:
On Sun, Jul 17, 2011 at 01:11:19PM +0100, John Robinson wrote:
[...]
# dd if=/dev/zero of=test bs=4096 count=262144
262144+0 records in
262144+0 records out
1073741824 bytes (1.1 GB) copied, 2.5253 seconds, 425 MB/s
And there's a badblocks running on another drive also on the ICH10.
Having said that, I think mine's wrong too, I don't think my array
can really manage that much throughput. We should both be using more
realistic benchmarking tools like bonnie++:
Or simply pass the correct flags to dd — like oflag=direct, which will
make it do non-buffered writes.
That's still not realistic:
# dd if=/dev/zero of=test oflag=direct bs=4096 count=262144
262144+0 records in
262144+0 records out
1073741824 bytes (1.1 GB) copied, 117.434 seconds, 9.1 MB/s
Because this time we're doing a read-modify-write for every 4K block, or
at least a write for every 4K block. I can fix it up again to work in
stripe size amounts:
# dd if=/dev/zero of=test oflag=direct bs=1572864 count=683
683+0 records in
683+0 records out
1074266112 bytes (1.1 GB) copied, 18.3198 seconds, 58.6 MB/s
But it's still not realistic because real I/O does use buffers and
doesn't work in magic sizes, so we should be using a more realistic
benchmarking tool like bonnie++.
Cheers,
John.
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