On Tue, 25 Sep 2007, Ralf Gross wrote:
Ralf Gross schrieb:
What do you get when (reading) from the raw device?
dd if=/dev/sda bs=1M count=10240
The server has 16 GB RAM, so I tried it with 20 GB of data.
dd if=/dev/sdd of=/dev/null bs=1M count=20480
20480+0 Datensätze ein
20480+0 Datensätze aus
21474836480 Bytes (21 GB) kopiert, 95,3738 Sekunden, 225 MB/s
and a second try:
dd if=/dev/sdd of=/dev/null bs=1M count=20480
20480+0 Datensätze ein
20480+0 Datensätze aus
21474836480 Bytes (21 GB) kopiert, 123,78 Sekunden, 173 MB/s
I'm taoo tired to interprete these numbers at the moment, I'll do some
more testing tomorrow.
There is a second RAID device attached to the server (24x RAID5). The
numbers I get from this device are a bit worse than the 16x RAID 5
numbers (150MB/s read with dd).
I'm really wondering how people can achieve transfer rates of
400MB/s and more. I know that I'm limited by the FC controller, but
I don't even get >200MB/s.
Ralf
Perhaps something is wrong with your setup?
Here are my 10 raptors in RAID5 using Software RAID (no hw raid
controller):
p34:~# dd if=/dev/md3 of=/dev/null bs=1M count=16384
16384+0 records in
16384+0 records out
17179869184 bytes (17 GB) copied, 29.8193 seconds, 576 MB/s
p34:~#
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