Re: Understanding bonnie++ results

Franck Routier wrote:

Hi,

I am experimenting with Adaptec 31205 hardware raid versus md raid on
raid level 10 with 3 arrays of 4 disks each.
md array was created with f2 option.
I get some results with bonnie++ tests I would like to understand:

- per char sequential output is consistantly around 70k/sec for both
setup
- but block sequential output shows a huge difference between hw and sw
raid: about 160k/sec for hw versus 60k/sec for md. Where can this come
from ??

  

Do you have a base raw read speed for a single drive? That helps visualize things as percentages of single drive speed. Also, is the Adaptec hw raid10 really raid1+0 or the distributed raid10 done by Linux sw raid?

On the contrary, md beat hw on inputs:
- sequential input show 360k/sec versus 220k/sec for hw
- random seek 1350/sec for md versus 1150/sec for hw

So, these bonnie++ tests show quite huge differences for the same
hardware between adaptec's hardware setup and md driver.

Does anyone has any explanation on this ? (btw, the fs on top of this is
xfs).

  

I'm sure that's a factor, but I usually run my tests on the raw array first to see how the array performs, then test on various filesystem types to see how they use the array. Alignment of the f/s on the array becomes important, as well as f/s-specific tuning parameters. Someone adept at xfs optimal layout will have to help you there, I can't.

-- 
Bill Davidsen [off-list ref]
 "Woe unto the statesman who makes war without a reason that will still
 be valid when the war is over..." Otto von Bismark