FreeBSD MySQL still WAY slower than Linux

[Martin Nilsson]

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