How do I split the data files into 2 hardisks?

Hi all,

I like this mailing list, very helpful.
I have a question regarding splitting data file to more than 1 hardisks.

Currently I have 2 x 2 GB hardisks.
I would like to split files in directory
/usr/local/pgsql/data/base/databasename
to 2 hardisks.

The reason is I want to dump 3 GB ~ 4 GB of data from oracle to postgres to
do testing.
I want to know whether postgres can handle 3 GB ~ 4 GB data, and so some
performance benchmarking. ( Oracle vs Postgres )

I don't have one 4 GB hardisk, so I have to split them.
I am using Linux.
Could any one help me ?

Thanks

Regards
Chai