Zones are the core units of redundancy in a Drobo disk pack, the critical protections against a fatal loss of data. The Drobo combines regions from multiple drives to create a redundant zone.
Zones can create either one or two additional copies of the data, depending upon if zones are single disk redundant or dual disk redundant. Dual disk redundancy means that the system can sustain two drive failures and would have to fail three drives before a fatal loss of data occurs.
Different types of zones using different levels of protection are automatically created within a disk pack to use all available drive space in the best possible way. Zones of different types and sizes can use regions from any drive, optimally allocating available capacity and optimizing performance. Drobo’s ability to use different zone types concurrently also allows dynamic adjustments to changes in the topology of a disk pack, such as adding or removing a drive, or drive failure.
When the topology of a disk pack changes, BeyondRAID automatically creates new zones and converts zones between types. Drobo incorporates new drives into a disk pack or returns to a fully redundant state. In the case of new drives, Drobo may rebalance a zone so that it is organized more efficiently across the available set of drives. This process involves creating a new zone with new regions, copying the data to the new zone, and then freeing the old regions.