problem creating log

[James Rich <james@xxxxxxxxxxxxx>]

When I create a log like this:

mkfs.xfs -l logdev=/dev/sdb6,size=10000b /dev/sda2

I get an error that says the size 10000b specified for log subvolume is
too large, maximum is 7 blocks.  If I leave off the size=10000b then I get
an error saying that 7 blocks is too small, minimum is 512.  I get this
error whether I use an external log or internal log.  mkfs.xfs -V shows:

mkfs.xfs version 2.0.3

what should I do?

James Rich