A Storage Array Snapshot is a logical point-in-time image of another volume, called a base volume. A snapshot is the logical equivalent of a complete physical copy, but you create it much more quickly than a physical copy and it requires less disk space.
Key Features of Snapshots
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Data Replication can be call many name by different vendors although they all are designed to do basically the same function transfer data from one place to another.
EMC's Symmetrix Remote Data Facility (SRDF) has 4 modes Synchronous (SRDFE/S), Semi-Synchronous (SRDFE/A), Adaptive Copy - Write Pending (SRDFE/AR) and Adaptive Copy - Disk (SRDFE/DM). The choice basically depends on whether you want the best possible performance, or to be absolutely sure that your data is consistent between sites. SRDF protects against local and regioal site disruptions, allows for continous data availability, multiple remote recovery sites, it supports multiple service levels with tiered storage and allows organizations to meet regulatory requirements. With SRDF you can migrate, consolidate, or distribute data across storage platforms. SRDF enables fast recovery from application restart and business to resume as normal.
IBM's Metro Mirror and Global Mirror are two types of remote-copy operations that you can use to set up a relationship between two volumes. The updates made to one volume are mirrored on the other volume.
Metro Mirror is a method of synchronous remote data replication that operates between two sites. Metro Mirror replication maintains identical data in both the source and target. When a write is issued to the source copy, the changes that are made to the source data are propagated to the target before the write finishes posting.
Global Mirror is a method of asynchronous remote data replication that operates between two sites. It maintains identical data in both the source and target, where the source is located in one storage system and the target is located in another storage system. The data on the target is typically written a few seconds after the data is written to the source volumes. When a write is issued to the source copy, the change is propagated to the target copy. However, subsequent changes are allowed to the source before the target verifies that it has received the change.
SAN Volume Controller and Storwize storage systems provide Metro Mirror and Global Mirror functions. Similarly, XIV systems provide synchronous or asynchronous mirror functions. Tivoli Storage FlashCopy Manager for VMware can back up the source or the target volumes on Metro Mirror, Global Mirror, synchronous or asynchronous mirrors.
NetApp’s SnapMirror offers an efficient data replication solution between storage endpoints whether flash, disk, or cloud. SnapMirror technology works with any application in both virtual and bare metal environments and in multiple storage configurations. SnapMirror leverages NetApp ONTAP® storage efficiencies by sending only changed blocks over the network. SnapMirror also uses built-in network compression to accelerate data transfers and reduce network bandwidth utilization by up to 70%.