Turn off Linux file cache

When mounting your hard drives use -o sync which will turn off write buffering for the drive.

You can also set it up in your fstab:

/dev/sda1    /    reiserfs        sync    0   0

For a plain hard disk it would normally be

hdparm -W 0 /dev/sdX

but RAID controllers typically don't pass that through.

You'll have to check the configuration interface of your RAID controller for any options. It might not be possible.