Symmetrix disk arrays are EMCs top tier offering in the enterprise storage segment.

EMC debuted their Symmetrix line of arrays in 1994 as a push to capture market share in the disk sub-system market for IBM S/390 mainframes. The original offerings came with either SCSI or IBMs own Enterprise Systems Connection (ESCON) interface. Symmetrix arrays rapidly gained popularity due partially to the fact they offered much greater performance than other storage cabinets of the time, especially among industries that needed the increased disk sub-system speed.

While modern PCs easily facilitate the ability to run RAID arrays via a controller card (onboard or add-in) and two or more drives, the requirements for enterprise class storage are much more demanding. Not only in capacity and throughput but also managing such large amounts of data and the ability to interface with enterprise servers from different manufacturers.

Even though there are far greater demands placed on this class of hardware, its easy to see where the trickle down of this technology has brought us cheap and easy RAID for consumer use.

Generally the schematic layout of these systems has multiple Fibre, SCSI or SATA drives occupying a 'shelf' or tray (also called a DAE or Disk Array Enclosure) containing a given amount of "slots". The shelf is connected to a device called a SPE (Storage Processing Engine) which handles the I/O functions on the shelf side and interfaces with the cache on the other side.

On the consumer scale the SPE and cache are integrated into a single card and in the case of most on-board solutions, the cache is omitted and the logic of the SPE is performed in software.

The last main piece of hardware is the Director which provides the connection to the host machine. This can be Gigabit Ethernet, iSCSI, Fibre Channel, ESCON or FICON depending on the machine an array is being attached to.

To date seven generations have been brought to market.