Three ways to consolidate

Storage consolidation means different things to different people. The main distinction involves the type of products you use to achieve consolidation, which, in turn, will determine the pool of possible vendors available to help. Three types of consolidation approaches exist, though some strategies can employ elements of each.

1. Big box

To some, consolidation translates into moving the data stored on many small disk arrays to one large array that offers many connection points. The shared array can be partitioned via software to segregate data from different business units or projects, and connections to the array can be allocated to specific servers and partitions.

2. Network-attached storage

Another approach is to reposition data from an internal server disk or direct-attached arrays onto network-attached storage (NAS) appliances. NAS appliances are essentially thin-server operating systems optimized for network attachment and storage processing and bolted to a disk array.

Most NAS boxes feature an appliance head, where the NAS operating system resides, and a set of trays, where disk drives are located. The appliance can scale vertically, by adding more trays, or horizontally, by adding more NAS to a TCP/IP network.

To enhance NAS appliances' scalability and to eliminate chokepoints that may result from too much vertical scaling -- or the management headaches that arise because of too much horizontal scaling -- vendors such as Silicon Graphics Inc. and others are introducing

NAS head clustering, which combines multiple NAS heads into one virtual head.

NAS also can be deployed to serve as a gateway to a back-end storage-area network (SAN), providing potentially enormous vertical scalability. This is one strategy Network Appliance Inc. officials are pursuing.

3. Storage-area networks

Storage consolidation also can be achieved through the use of a SAN. Technically speaking, these are more appropriately referred to as channel fabrics in which a switch is placed between a server and a direct-attached storage array that makes and breaks point-to-point high-speed connections.

SANs enable the interconnection of hundreds of thousands of nodes, which are servers and storage devices, and facilitate the aggregation of storage. Consolidation, in this usage, refers to putting all data into one entity -- the SAN -- that fewer individuals can then monitor and administer.

Adding virtualization software to any of these platforms provides a means to allocate and reallocate storage to specific applications. Virtualization hides the technical complexity involved in assigning physical storage resources such as disk space to specific applications. To many vendors, virtualization is the only path to true consolidation.