Forcing a flush, disableing hdd cache

[Dan Browning]

How do I force Linux (2.2.5, on rh6) to flush the hard drive cache?
Seperately, how do I disable the cache and force all writes to be immediate?

I am wondering because of scenarios when a power outage might be
emminent-but I cannot shut down the box.  Hopefully flushing and disabling
the cache would reduce data-loss after the outage.

What other steps should be taken to ensure data safety during such a
scenario?  Thanks for the help,

Dan Browning
Network Administrator
Cyclone Computer Systems