EV Exchange journaling closed partition erased from disk after tape backup

Hi all,
our situation is the following: we have EV8 sp2 running with 2 different vault stores, one for exchange 2007 archiving and the other for file system archiving. Both vault stores are in the same vault store group with sharing level enabled within the entire group.
We are archiving exchange journaling in the same vault store used for user mailbox archiving.
Now we'd like to create a new vault store within the group and use it for journaling archiving, using more partitions mounted via network share for automatic rollover. Within this partinion we won't enable collactions.
When every year the partion rollover will occour we want to backup the closed partition to tape and the erase data from disk. In case we need to search in journaling archive for data not available on disk we can schedule a manual restore.
Is it possible to do that? How does EV works when a closed partition is currently defined and indexed but data has been removed from disk?
Thanks in advance.
Regards,
Andrea Donaggio