Is there a performance advantage of adding a second parity set?

[rob@xxxxxxxxx]

We have a system with 17 drives.  We are going to add six 70GB drives.  If 
I add them two at a time they will add them to the existing parity set. If 
I add them all at once it will start a new parity set.  Starting a new 
parity set effectively ties up one of the 70GB drives to raid striping. We 
really don't need the space though - we just have 70GB drives laying 
around.  Without the new drives we are only at 50% used.  The existing 
parity set has the striping across 8 drives.  I take it the new set would 
have the striping across 4 drives?

These six 4327's would go into a 5787.  Into P1-D1 through P1-D6.
P1-D7 through P1-D12 are 4328's.  P2-D1 through P2-D5 and P2-D7 through 
P2-D11 are 4328's.  Leaving P2-D6 and P2-D12 open.

Rob Berendt