Firmware upgrades don't usually cause volumes to disappear, so you probably need to troubleshoot this from a "missing volume" point of view.
Depending on the disk configuration you were using - Volume_2 could have been the second hard drive, or, a partition on either drive - so start there - tell us what disk configuration you had - standard volumes, or some form of RAID.
Also, log into the management interface and check the disk status - does it show both disks?