How to allocate 8 disks

We're upgrading to a medium-sized server, a Dell PowerEdge 2950, dual-quad CPU's and 8 GB memory.  This box can hold at
most8 disks (10K SCSI 2.5" 146 GB drives) and has Dell's Perc 6/i RAID controller. 

I'm thinking of this:

  6 disks  RAID 1+0  Postgres data
  1 disk   WAL
  1 disk   Linux

I've often seen RAID 1 recommended for the WAL.  Is that strictly for reliability, or is there a performance advantage
toRAID 1 for the WAL? 

It seems to me separating the OS and WAL on two disks is better than making a single RAID 1 and sharing it, from a
performancepoint of view. 

Thanks,
Craig