gpt backup header?

[Steven Bellovin <smb%cs.columbia.edu@localhost>]

I decided to convert a disk from fdisk/mbr to gpt/wedges; however, gpt muttered 
that there was no room for a backup header.  (a) Is this a problem?  (b) If so, 
what should I do to solve it?  This is on amd64/5.1rc2.

# fdisk wd3
Disk: /dev/rwd3d
NetBSD disklabel disk geometry:
cylinders: 3876021, heads: 16, sectors/track: 63 (1008 sectors/cylinder)
total sectors: 3907029168

BIOS disk geometry:
cylinders: 1023, heads: 255, sectors/track: 63 (16065 sectors/cylinder)
total sectors: 3907029168

Partition table:
0: NetBSD (sysid 169)
    start 63, size 3907029105 (1907729 MB, Cyls 0-243201/80/63)
        PBR is not bootable: All bytes are identical (0x00)
1: <UNUSED>
2: <UNUSED>
3: <UNUSED>
Bootselector disabled.
No active partition.
# gpt create wd3
gpt: rwd3d: error: device contains a MBR
# gpt create -f wd3
gpt: rwd3d: error: no room for the backup header

                --Steve Bellovin, http://www.cs.columbia.edu/~smb