Restoring data to a distributed storage node

#1. Field of the Invention

#The present invention relates generally to data storage systems, and specifically to methods for managing storage systems providing data redundancy.

#2. Description of the Related Art

#FIG. 1 is a schematic block diagram of a data storage system, according to an embodiment of the present invention;

#FIG. 2 is a schematic diagram of a mapping used in the system of FIG. 1, assumed to be in tabular form, according to an embodiment of the present invention;

#FIG. 3 is a schematic diagram of a location table, according to an embodiment of the present invention;

#Reference is now made to FIG. 1, which is a schematic block diagram of a storage system 10, according to an embodiment of the present invention. System 10 provides data storage for one or more hosts 12, which are coupled to the storage system by any means known in the art, for example, via a network such as the Internet or by a bus. Herein, by way of example, hosts 12 and system 10 are assumed to be coupled by a network 14. Storage system 10 typically operates in, or as, a network attached storage (NAS) or a storage area network (SAN) system. However, it will be understood that the scope of the present invention is not limited to storage systems operating in any particular configuration. Rather, the scope of the present invention includes systems operating in any suitable configuration used for storing data.

#Storage system 10 comprises one or more storage nodes, indicated in FIG. 1 as nodes 24, 26, and 28. However, it will be appreciated that the number of nodes used in system 10 may be any convenient number. Nodes 24, 26, and 28 are distinguished from each other to facilitate the exposition of node operation hereinbelow. All nodes in system 10 are assumed to operate in substantially the same manner and to comprise substantially similar elements.

#Each of nodes 24, 26, and 28 is assumed to comprise a set of physical storage 22. Each set of physical storage comprises multiple slow and/or fast access, non-volatile, mass storage devices, hereinbelow assumed to be multiple hard disks. Each of nodes 24, 26, and 28 is also assumed to comprise a communications interface 18, which performs the task of communicating with other elements of the data storage system. A data storage node may also comprise a cache 20 that provides a fast source of recently accessed data, typically saved in Random Access Memory (RAM). Typically, a data storage node also comprises a node processor 21 and a source of executable software, not shown in the figure. It will be appreciated that actions performed by a node as described hereinbelow are implemented by the node processor.