I'm planning to install a DRBD device on a (replicated) disk with two GPT partitions. DRBD requires some space for (preferentially "internal") metadata at the end of the underlying device. I'm hesitant to leave this space unpartitionend (or unformatted in a normal partition). I'd like to reserve an extra partition at the end of the underlying disk device for the metadata. (If I understand correctly, DRBD would not care about the partition or its type and could then use that space exclusively.) My question is:

Which would be a suitable GPT partition type for such a metadata partition?

• It should not be a type interpreted while booting (such as EF00 EFI System).
• It should not be a type prone to be modified accidentialy by the booted OS (such as 8200 Linux swap, 8e00 Linux LVM, fd00 Linux raid). (The booted OS will be Ubuntu Linux 12.04.3.)
• It should not be a type indicating a normal filesystem (such as 0c01 or 8301), prone to be formatted correspondingly.
• It should not be a type requiring any special content in the partition (since the content is to be handled exclusively by DRBD).
• It should express the purpose of being reserved for something special (namely DRBD).

(The types I listed are as provided by gdisk. I'm thinking about using some type unlikely to be used by the OS (maybe bf0a Solaris Reserved 4) or an invented(?) type such as fd01 (close to fd00 Linux raid…). Would something like this be suitable, too dangerous or even possible?)