XFS + SMP + Software RAID 5 slow?

[Andrew Klaassen <ak@xxxxxxx>]

I've been experiencing *very* slow sustained write ( < .5MB/sec)
using 2.4.20-20.9.XFS1.3.1smp on a dual-Xeon box with a 3ware
7506 card in JBOD mode.  Software RAID 5.  No such problems with
Ext3 ( > 20MB/sec sustained write) with the same kernel on the
same software RAID 5 device.  Obviously there's something very
wrong here.

Known issue?  Any idea what might be causing this?

Andrew Klaassen