One of the plugins that is in a race to be stable 
before 2.6.14 is the compression plugin. That will
allow you to use half the space while increasing 
performance. 
Yes, increasing performance, because CPUs are 
powerful and compression algorithms are efficient
these days, and if you halve your IO it is good 
for performance. One of the keys to making this 
true is that we only compress at the time we flush 
to disk, rather than with every write, and that 
means that if you have a hot set of files that fit
into RAM, there is no performance loss because there
is no compression going on.