Time Machine problem

I have Time Machine backups for my MacBook Pro running 10.6.8 (Snow Leopard) on a 1TB external disk.

I've just obtained a 2TB external disk on which I've performed a Time Machine backup of my daughter's MacBook also running 10.6.8, and wanted to put a copy of my 1TB Time Machine backups on there so I have a duplicate should the 1TB disk fail, and also add backups of data (mainly music and photos) from other older Macs (not using Time Machine).

There is plenty of room for all these for some time to come, even on the 1TB disk - changes to the backed up data consists mainly of occasional iPhone backups with new photos. I don't want to partition the 2TB disk and am aware of the problems if I don't.

Trying to copy the Backups.backupdb folder from 1TB to 2TB by dragging between Finder windows fails and gives the message:
"The backup can't be copied because the backup volume doesn't have ownership enabled"

I can, apparently, copy the other way.

Sharing & Permissions is set to Read & Write for admin, Me, staff and everyone on the 2TB.

Should taking a simple copy as a further backup be possible? If it works from 2 TB to 1TB, why not the other way? Am I doing this incorrectly? The only instructions I can find relate to transferring TM backups to a new drive. I do not want to transfer, just take a copy.

Many thanks,
John