Lost Storage when install CM 10.1.3 I have problem when install CM 10.1.3 state. It looks like I've lost my storage: In stock ROM it has ~11 GB, but just 1.9 GB in new ROM :(.

Where is it gone to? What can I do to regain it?

I use Galaxy S2

 
Screenshots (click images for larger variants)
Did you backup your stock ROM prior doing the upgrade?  I had this happen to me where I backed up the current ROM to, what I thought was, the external SD card, but it was infact the built-in SD card.  The naming of endpoint exposed in CLockworkMod Recovery (CWM) led me to believe I was using the SD card.  I backups were not visible in the file explorer, needed to drop back into CWM to delete the bad backup and re-backup on the actual external SD card.