Roman Neuhauser wrote:
In all honesty, I'm getting somewhat irritated by all the
"dd is meaningless performance measurement tool, use something
real" and similar arguments: dd is a real command for real
work, and if it shows abysmal performance of sequential writes,
then there's a problem.
There _is_ something strange with dd as sequential block reads with
bonnie (and vfs.read_max=16) is faster than reading direct from the
device with dd!
RAID0 7*36GB Maxtor 10K4, MegaRAID 320-2E default newfs
-------Sequential Output-------- ---Sequential Input--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block---
5.4 2048 106839 84.7 115268 32.1 30204 9.0 78264 80.2 136833 21.5
5.4v 2048 105996 84.4 114560 32.2 29208 8.8 81671 84.7 227416 39.4
v = vfs.read_max=16
I don't have exact numbers at hand but
dd if=/dev/amrd0 of=/dev/null bs=1024k count=1024
gave about ~120MB/s not anywhere near 227MB!
/Martin
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