Sizing and striping log area

Forgive my ignorance, but what should I consider when sizing the partitionwhich houses the pg_xlog area? Are logs cleared out every once in awhileor do they continue to accumulate? Let's say your DB is around 4 GB,what should the log area size be, or does the size of the DB not matter,if not which factors should be considered?
Also, on a related note, would putting the pg_xlog onto a RAID-0 arrayimprove performance much? Striping seems great for parallelizing seeks,and seeks are, if I recall, the main bottleneck for disks. But since thelogs are written in a serial manner, there should be little to no seeking soperformance gains wouldn't be all that much compared to dedicatedsingle disk logs?
Now straying even further from the original subject... Would hardware vssoftware RAID 0 not make a difference in reality? Software stripingincurs CPU and SCSI bandwith overhead. But in production CPUshouldn't in theory be more than around 50% or so, if so there's acapacity issue and you should consider upgrading CPU. And withmost modern SCSI cards, bandwith is much greater than diskspeed, so the extra overhead wouldn't make much difference. Thismight explain the popularity of Veritas.
Thanks for any help.

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