Symmetrix Remote Data Facility

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The Symmetrix Remote Data Facility ( SRDF ) is a software for enterprise storage company EMC ². Today it is considered the standard of enterprise applications and business processes for uninterrupted operation. SRDF mirrored (copied) automatically and in real time the dataset of a primary Symmetrix storage system in a second, spatially separated Symmetrix storage system.

SRDF originally describes a technique for the replication of logical devices between two remote EMC ² Symmetrix storage systems. A distinction is made between synchronous replication ( SRDF / S) and asynchronous replication ( SRDF / A). It was launched by EMC on the market in 1993. Meanwhile, the technique is also used to replicate between a Symmetrix storage and another SAN or IP address.

Operation

SRDF sets logical pairs determined by a Logical Unit Number (LUN) or a group of LUNs from each disk array and replicates data from one to another synchronously, semi- synchronously or asynchronously. Can an established pair of LUNs can be split so that separate machines present the same data and use them independently (eg for backup). After that, the asynchronous state can be synchronized again.

In synchronous mode ( SRDF / S) waits for the primary array on to the secondary array has performed and confirmed each write operation before writing the next write operation triggers. Thus, the replicated copy of the data is always as current as the primary. However, the resulting latency increases significantly with the increasing distance between the replication sites.

In the semi- synchronous mode, the application receives the confirmation of the first write operation from the local cache. The second write operation is performed only if the previous write operation has been confirmed by the remote cache. This form of SRDF is faster than the synchronous mode.

Asynchronous SRDF ( SRDF / A) replication to the secondary array are included in the delta sets that are transferred at defined intervals. Although the remote copy of the data is never as up to date as the primary copy, this method can be applied replication of data over long distances and with reduced bandwidth requirements.

Other forms of SRDF implementation exist to integrate these into cluster environments and multiple replication pairs to keep in sync multiple LUNs as in the data and log files of a database application.

Applications

• Data Warehousing
• Balance of databases in the groupware
• Data Migration
• Disaster Recovery