Where should my data go?

At the moment, I store my data in 3 places:

• Windows and programs run from a single 300GB hard drive (which I would like to upgrade to a solid state drive sometime soon).
• My user folder is dumped onto a RAID-1 array of 2x 1TB disks.
• Drobo containing 4x 1TB disk, formatted to give 3TB (or 2.7 TiB) space.

The Drobo is the current centre of question, I’m now up to 85% used which doesn’t give me much room for expansion. The question is what to do now.

My Drobo is currently piped through a DroboShare, which limits its performance greatly, I generally don’t get more than 12MB/s from it, even across a gigabit network. While this is not bad from a network device, it isn’t ideal. One way to fix this performance is to upgrade to an FS.

Upgrade options:

• Start upgrading the disks in the disk pack, if I swap in 2+ 2TB disks I will be able to expand the storage to meet my current needs for the not to immediate future.
  This is a good choice as the future of storage is now uncertain, in the year that this method could bring, the storage market could have changed dramatically.
  This would give me between 4-6TB (3.6-5.5TiB) space.
   
• Upgrade to a Drobo FS, if I pick up a FS and 2+x 2TB disks, I would be able to get all of my data onto those and my user drive. I could then in turn sell my older Drobo with the old disks as a full storage solution to make back some of the money I would loose in the upgrade.
  This is a good choice as I would then have 3 bays to fill with 2tb disks as my storage use expands. A Drobo FS should achieve about 50MB/s transfer.
  This would give me between 2-8TB (1.8-7.3TiB) space and 4x speed.
   
• Switch to another storage solution that would be much cheaper to buy initially but be harder to upgrade/swap disks in the future.
   
• Rely on short term measures to keep the data load on the Drobo down, such as shuffling data or archiving data on a cheap USB external disk.