Hi,
Try /dev/random instead of /dev/zero. SSDs are known to use data
compression algorithms to run-length-encode drive data on the fly, to
increase bandwidth and reduce data replication on the drive. It's
possible that your drive is performing write optimization on your test
which is not applicable to the real world.
If you want a speed benchmark you probably want /dev/urandom instad
of /dev/random, because /dev/random will block when it runs out
of high-quality random numbers.
I've used /dev/urandom output from a file
> dd if=/dev/urandom of=random.bin bs=1K count=10000000
> dd if=random.bin of=/SSD/test.bin bs=1K count=1000000
1000000+0 records in
1000000+0 records out
1024000000 bytes (1.0 GB) copied, 11.1116 s, 92.2 MB/s
> dd if=random.bin of=/SSD/test.bin bs=10K count=100000
100000+0 records in
100000+0 records out
1024000000 bytes (1.0 GB) copied, 9.74512 s, 105 MB/s
> dd if=random.bin of=/SSD/test.bin bs=100K count=10000
10000+0 records in
10000+0 records out
1024000000 bytes (1.0 GB) copied, 9.38715 s, 109 MB/s
> dd if=random.bin of=/SSD/test.bin bs=1000K count=1000
1000+0 records in
1000+0 records out
1024000000 bytes (1.0 GB) copied, 9.38381 s, 109 MB/s
> dd if=random.bin of=/SSD/test.bin bs=10000K count=100
100+0 records in
100+0 records out
1024000000 bytes (1.0 GB) copied, 9.29913 s, 110 MB/s
If I read directly from /dev/urandom the whole performance goes down
as random numbers can be generated fast enough....
Thanks,
Thomas
--
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Dr. Thomas Hobiger
Space-Time Measurement Project
Space-Time Standards Group
New Generation Network Research Center
National Institute of Information and Communications Technology
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