RE: FTP bottleneck

Rob, 

Possible bottlenecks:

LAN: It's actually Gb Ethernet and not GB.  The absolute total best
throughput you're like to be able to do is around 100-120MB/sec out of
the adapter.  Other factors include the packet size (1496 or 8996; 8996
is better if doing mostly large transfers but make sure your networking
gear fully supports it) and IP buffer sizes (CHGTCPA; here we use
1048576 for both send & receive buffer sizes).

System Frames: 2GB/sec HSL2 on modern hardware so that's a very low
possible area of concern.

RAID card: Ultra320 SCSI so 320MB/sec max for each SCSI channel (I think
2757/2780 controllers have 2 channels).

Disks: I don't think there's any single hard drive on the market so far
that can sustain over 100MB/sec (they can burst the full 320MB/s of the
SCSI interface but sustained is far less).  Most will top out around
70-80MB/s under optimal conditions.  Granted, I haven't followed this
closely the past couple of years but I believe that to still be the
case.  With scatter-loading this is less of a factor, however you're
noting the drives being 20+% busy so they're likely servicing other
requests and cannot sustani max throughput for your large file reads.

FTP job resources/system CPU: I'm not sure what kind of bandwidth is
possible in the CPU but I'm pretty sure you're nowhere near saturating
it in this case.

Going for the low hanging fruit, I'd check the LAN settings first.