Create a single disk from multiple externals

With a RAID configuration this is possible.

 

To use drives of different sizes - this is a good solution. You can mix and match drive sizes and it shows up as one volume - in a easy-to-use redundant solution.

Starts at $399.

www.drobo.com

 

I've seen some of these comments, but I've been using a Drobo for a while with no issues. There are definitely a few solutions out there.

 

With the keyword "reliable" I'd say "no". RAID won't work with differing drive sizes and while you can do a "concatenated disk set" with Disk Utility if any drive fails you lose everything.

Most external drives these days are sealed into their cases. If you can remove the drives a Drobo would work, but it is likely too expensive a solution to salvage what are probably a collection of small and fairly worthless (based on 2TB drives <$100 these days) drives.

Edited to add the "start over" approach. Toss those existing drives. Then you can buy a dual drive housing capable of RAID (if you wish) from OWC for $100 http://eshop.macsales.com/item/Other%20World%20Computing/MEPQ936AL2/, and add two 3TB Hitachi drives from Newegg for $260. That would give 6GB capacity for less cost than the bare Drobo alone. That ought to hold you a while!

 

You can create a software RAID disk in the Disk Utility, but there are some cons to this:

1. Its software RAID rather than hardware RAID, which isnt as reliable or fast.
2. The discs need to all be the same size.
3. While RAID creates redundancy, you're more likely to have problems with the RAID set as a whole as every external drive you add adds to the increased risk of failure.
4. You havent mentioned backing this large, distributed volume up which is basically just asking for trouble!

If you dont have the money to go out and buy a dedicated RAID box or Drobo you may be better of just using half the discs for storage, then use the rest of them for automated frequent backups (i recommend Carbon Copy Cloner)

 

I have used the built in software RAID successfully in the past to do just that, consolidate four externals into bigger storage volumes. What I experienced, though, was that for USB drives anything more than 2 in a RAID (either 1 or 0) set was prone to frequent corruption. So I did sets of two which provided enough volumes to have a primary and a backup in case of RAID or disk failure. Of course it takes alot of USB ports to have that all running. After about 6 months running like that, I went with OWC enclosures to reduce power and port needs.