had this p520 server connected to a DDS-3 4mm tape drive...
running AIX 7.1 TL01 -- the latest release.
mksysb -i -e /dev/rmt/1 ..tells me only 1% is done after over an hour ...
I had no problems with th hardware and other connections...
tar command to /dev/rmt/1 runs very fast ....
tape block size is default to 512 bytes..