mklv(1M) help on 3.3.1

[Kevin D. Baranski-Walker]

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I'm desparately attempting to extend my /usr partition:

	1) mkfs new disk /dev/dsk/dks0d4s7 (the whole efs disk)
	2) create /etc/lvtab;
	
	 	lv1:extended-usr-partition:stripes=2:devs= \
			/dev/dsk/dks0d1s6, /dev/dsk/dks0d4s7
	
	3) take the system down to single user
	4) mklv lv1;
		and I get <INCORRECT PARTITION SIZE> for /dev/dsk/dks0d4s7
	

What am I missing?  Can is it legal to make a lv from a 'live' partition (i.e.,
/usr)?

Thanks in advance,

- kevin