As per below link illegal requests are considered as soft errors. so it might not be issue with h/w.
http://blogs.sun.com/chrisg/entry/iostat_e_whats_that_all you could try DTrace tool kit iosnoop and iopending and hotspot for spotting what's happening with disks. run cp command in background try iosnoop on that. -- This message posted from opensolaris.org
