# when to use hdparm tweaks on raid array

## taskara

hey,

I'm wanting to raid my two 40 gig hdds, I am wondering when I should use some hdparm tweaks, or whether it doesn't matter at which stage.

And do I use them on /dev/hde or on the /dev/md  ??

I did read that you sohuld tweak hdparm B4 you make fs and compile your system..

ta  :Smile: 

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## rojaro

yo,

well, i actually use hdparm for only one thing - setting udma mode from 33 to 100 mhz on a first generation CMD 649 controller, but normally you don't need the hdparm tool, as most drivers (e.g. promise or intel PIIX) configure the controllers correctly on their own.

anyway, as the hdparm tool is designed for use with physical devices (like harddrives) you can't use it with virtual ones like /dev/mdX.

and yes, you should use it before compiling IF your controller isnt correctly configured, e.g. it's using 33 mhz instead of 100 mhz. and well, 100mhz are a lot faster ... 

there is also a very good man-page for hdparm ... man 8 hdparm

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## taskara

thanks for the tips.. I thought that was the case because most people seem to have high hdparm results..

testing the diff between a "software" raid controller like promise onboard, compared to speed and cpu usage with linux controlled software raid..

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