following this advice
http://parted.alioth.debian.org/cgi-bin/trac.cgi/ticket/195
exclude md devices from the block list wich have a partition

md devices will no more be reported by 'print devices'
before
parted /dev/hda print devices
/dev/hda (2625MB)
/dev/hdc (6488MB)
/dev/md0 (805MB)
/dev/md1 (1818MB)

after
parted /dev/hda print devices
/dev/hda (2625MB)
/dev/hdc (6488MB)

this does not change the behavior with
parted /dev/md0 print
Error: Can't have a partition outside the disk!

diff --git a/libparted/arch/linux.c b/libparted/arch/linux.c
index 6e47107..37ed3aa 100644
--- a/libparted/arch/linux.c
+++ b/libparted/arch/linux.c
@@ -1976,6 +1976,7 @@ _skip_entry (const char *name)
 		{ "..",		sizeof ("..") - 1	},
 		{ "dm-",	sizeof ("dm-") - 1	},
 		{ "loop",	sizeof ("loop") - 1	},
+		{ "md",		sizeof ("md") - 1	},
 		{ "ram",	sizeof ("ram") - 1	},
 		{ 0, 0 },
 	};