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The Symmetrix system was an EMC Corporation's enterprise storage disk array. It combined dozens of into a single virtual device that was then directly attached to a computer or I/O channel, or shared on a storage area network or a local area network. It was the flagship product of EMC in the 1990s and 2000s.
This product is the main reason for the rapid growth of EMC in the 1990s, both in size and value, from a company valued hundreds of millions of dollars to a multi-billion company.EMC Company Web site, July 19, 2000 "EMC Reports 43% Growth in Storage Revenue, First $2 Billion Quarter" Retrieved October 24, 2010. Moshe Yanai managed the Symmetrix development from the product's inception in 1987 until shortly before leaving EMC in 2001, and his Symmetrix development team grew from several people to thousands.
The Symmetrix VMAX system bay can hold one to eight engines. These engines house the hardware for all the data processing capabilities. Each engine contains two director boards, memory chips, and front-end (FE) and back-end (BE) ports for connectivity to hosts and storage bays, respectively.
Each director board contains two Intel quad-core processors for data processing, 16, 32 or 64 GB of physical memory, one System Interface Board (SIB) that connects the director to the Matrix Interface Board Enclosure (MIBE), front-end and back-end ports.
The VMAX has one to ten storage bays for hard drives. Each storage bay contains 16 Disk Array Enclosures (DAE). Each DAE contains 15-25 hard drives. VMAX supports SATA, Fiber Channel, SAS and Solid State drives.
SRDF logically pairs a device or a group of devices from each array and replicates data from one to the other synchronously or asynchronously. An established pair of devices can be split, so that separate hosts can access the same data independently (maybe for backup), and then be resynchronised.
In synchronous mode (SRDF/S), the primary array waits until the secondary array has acknowledged each write before the next write is accepted, ensuring that the replicated copy of the data is always as current as the primary. However, the latency due to propagation increases significantly with distance.
Asynchronous SRDF (SRDF/A) transfers changes made to the secondary array in units called delta sets, which are transferred at defined intervals. Although the remote copy of the data will never be as current as the primary copy, this method can replicate data over considerable distances and with reduced bandwidth requirements and minimal impact on host performance.
Other forms of SRDF integrate with clustered environments and to manage multiple SRDF pairs where replication of multiple devices must be consistent (such as with the data files and log files of a database application).
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