If you attempt to create a rootvg WPAR with a VSCSI disk, on a system running AIX 6.1 TL6 and you encounter the following error:

# mkwpar O -D rootvg=yes devname=hdisk5 -n rootvgwpar1

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ERROR

mkwpar: 0960-587 hdisk5 has un-supported subclass type.

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Then you should check that the following filesets are installed:

# lslpp -L | grep wio
wio.common 6.1.6.0 C F Common I/O Support for
wio.fcp 6.1.6.0 C F FC I/O Support for Workload
wio.vscsi 6.1.6.0 C F VSCSI I/O Support for Workload

Once these filesets are installed (from the AIX 6.1 install media), then you should be able to create a rootvg WPAR using a VSCSI disk.