Recovering shared folder contents from tar.gz backup?

[Kővári János]

Hello everyone!

Something has happened with one of my cyrus servers, which was hosting 
one shared folder (with multiple subfolders in it). I still don't know 
what has happened - most likely a mailboxes.db corruption, no idea why. 
Since this is automatically backed up every 4 hours or so, it's gone - I 
only have backups of this in an already corrupt state (assuming the 
problem was corruption of this db)
I tried fixing things with reconstruct, but it didn't help, the shared 
folder disappeared permanently, even though all the files are still in 
the storage partition.
I have regular backups of the mail storage (simple tar.gz of the whole 
structure), so nothing is lost.
Since all my attempts to recover the shared folder were unsuccesful, I 
decided to wipe this partition and recreate it, with the exact same 
structure, then tried copying back the data from a backup and then 
reconstruct, but this didn't help at all, the recreated shared folder 
still shows up as empty, reconstruct doesn't find the subfolders etc.
Could someone please tell me how to get my mail back frum the backup?
Thanks in advance!

Regards,
Janos