What seems to be the problem? RAID has been a boon to physical data protection, but one of the requirements of traditional RAID is all the drives in the same RAID group have to be the same fixed size. For very small organizations (including parts of larger organizations) that need to add just one or a few different-sized drives over time or who have mismatched drives now that means that they cannot take advantage of RAID. 

What do you need to know? Data Robotics has an interesting answer. (Data Robotics gave me an analyst briefing on their product.) Drobo is an appliance that will fit up to four drives in a small box. Drobo plugs into a USB port. A user simply slides a new 3.5” SATA drive of whatever size capacity (although bigger is better) into a slot in the appliance (which Data Robotics characterizes as a storage robot). The drives can be any mix of brand, size, speed, and capacity.

The new drive does not have to be tabula rasa (i.e., blank), but it might as well be because anything on it will be erased as it becomes part of the data protection storage pool. Drobo uses a proprietary means of parity protection that moves data around and protects the data in a RAID-like manner.

Ease of use is an often misused phrase, but not in this case. The storage robot is targeted at someone who has no technical storage or storage management expertise whatsoever. For example, no application software is required. The appliance senses a new drive and automatically does its re-configuration thing. Drobo uses a traffic light analogy. Three simple lights communicate to the user what, if any, action, needs to be taken. When the lights are green, the data is safe. When the lights are yellow, the appliance is 85% full. Your choices then are to add a drive (if you still have a slot left) or replace an existing drive with a larger capacity drive. However, you have time to do that. That is not the case when red lights appear. In that case, addition or replacement of a drive must be done immediately. Note that in all cases where action has to be taken is that the actions are to either replace an existing drive or add a new drive. The user interface does not require a computer console on which a command is given.

Please note that the data protection is for physical disk protection against disk failures. As with standard RAID, no data protection exists against other physical threats, such as fire, flood, or hurricanes. Moreover, there is no protection against logical data protection problems, such as viruses or accidental deletion of data that you did not want deleted. But the approach does solve the direct disk failure problem, which is a key data protection problem.

What can you do about it? The storage industry continues to bubble with innovative ideas. Enabling the mixing and matching of different size drives for parity-protected storage is one of those clever new ideas. If your organization would benefit from mixing and matching drives, you may want to give this concept a greater look.