-        EMC Symetrix with Timefinder (volume) or EMC Snap (data set)

-        IBM ESS with Flashcopy (V1 for volume, V2 for data set)

-        IBM PPRC (volume—within same enclosure; PPRC technology is supported by EMC, Hitachi Data Systems, and StorageTek)  

-        HDS ShadowImage (volume)

-        StorageTek Snapshot (pointer-based volume or data set).   

Remote replication is based on storage devices or processes that replicate updates to an alternate site as they occur (synchronous) or soon thereafter (asynchronous). Typical data loss is almost zero for synchronous solutions. Synchronous solutions are distance-sensitive. Typically, a synchronous mirror must be within 100km to eliminate local performance degradation. These solutions might be envisioned as a “campus” environment. Some examples of synchronous remote mirroring include:   

-        EMC Symetrix SRDF/S

-        IBM PPRC (also supported by EMC, HDS, and STK devices)

-        StorageTek PowerPPRC.

Asynchronous solutions exist to allow for an extended-distance, remote site location, but care must be taken to ensure the remote site data consistency. For that reason, some of the technologies involve an intermediate “hop” site or volume as part of the replication process, timestamp the I/O to the remote site, or use other techniques to ensure consistency. Some examples of asynchronous remote mirroring include:  

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