Migrating from MBR to GPT?

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

I've recently noticed that I have a 4TB disk in use of which I'm only
using 2TB.

# disklabel wd0 | tail -5
5 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a: 4294965247      2048       RAID                     # (Cyl.      2*- 4294967295*)
 c: 4294965247      2048     unused      0     0        # (Cyl.      2*- 4294967295*)
 d: 4294967295         0     unused      0     0        # (Cyl.      0 - 4294967295*)

Probably because it was set up with an MBR instead of a GPT:

# fdisk wd0
Disk: /dev/rwd0d
NetBSD disklabel disk geometry:
cylinders: 7752021, heads: 16, sectors/track: 63 (1008 sectors/cylinder)
total sectors: 4294967295

BIOS disk geometry:
cylinders: 1023, heads: 240, sectors/track: 63 (15120 sectors/cylinder)
total sectors: 3519069872

Partitions aligned to 15120 sector boundaries, offset 63

Partition table:
0: NetBSD (sysid 169)
    start 2048, size 4294965247 (2097151 MB, Cyls 0/32/33-284058/164/3), Active
1: <UNUSED>
2: <UNUSED>
3: <UNUSED>
Bootselector disabled.
First active partition: 0


I know that MBRs and GPTs conflict. Is there a way to migrate this
disk to a GPT so that I can make use of the remaining data (without
copying all the data off to a separate disk)?

Or is migrating to a GPT optional, and I can use the remaining space
in some other way?

Thanks,
 Thomas