mkfs.xfs, lvm, multi-terrabyte hardware array and luks

When I try to format partitions above 2-3gb my opteron experiences heavy io wait; the mkfs.xfs fails, and I receive the following....

 "mkfs.xfs: libxfs_device_zero write failed: Input/output error"

When I format partions below 2-3gb, there is no problem whatsoever.  I can mkfs.xfs on a +2-3GB non-luks formated partition without a problem... any thoughts?