Configuring PostgreSQL for write performance
1 Gigabyte a day is not that high of a write load.  Spread out throughout the day, that comes out to about 50kbytes a second. A slow USB thumb drive could handle that.  I'm assuming it's more bursty though.  As a_horse_with_no_name suggests, increase checkpoint segments.  100 or so is not out of the ordinary.

Then increase your checkpoint_timeout to 1 hour, as well as look at increasing your checkpoint_completion_target to something closer to 1.0 (100%).  The completion target tells PostgreSQL how aggressively to write in the background so that it's x% complete before running a checkpoint, which force all the data to be written out at once from the WAL and will slow the system to a crawl while it's happening.

The reason you don't usually set it to 100% is that it's pretty common to write to the same block more than once, and by delaying WAL writes out to the main store, you prevent the same block being written twice for no reason.

If it's unlikely you'll be writing to the same block more than once before your timeout occurs, i.e. all you do is insert then setting it pretty high makes sense to raise it to 0.9 or so.  The worst that'll happen is you'll write a little more often than you might otherwise need to, but checkpoints impact will be greatly reduced.