geli metadata backup

[Robert Simmons]

What exactly is contained in the metadata backup file /var/backups/_prov_.eli ?

Obviously, since I keep /var inside of the encrypted provider, the
default location is a bad place for a backup.  Where would a good
location be to save this metadata using the -B switch for geli init
other than the default?

I have /home /root /tmp /usr and /var inside the encrypted provider.
Everything else is unencrypted.