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The IBM XIV system includes near unlimited differential snapshots created instantly and with virtually no impact on performance as one of its standard no cost features.
The XIV system implements a revolutionary approach to all aspects of snapshot creation and handling, overcoming traditionally known drawbacks. This breakthrough is made possible through the system's fully scalable grid storage platform. Each snapshot-related process is performed over all modules concurrently and over all spindles system-wide.
Innovative (patent-protected) meta-data design - supports a practically zero-time snapshot creation process, because the size of the metadata used in the process is truly minimal. In fact, the IBM XIV system requires meta-data only per the total differences between the snapshot and the volume (or between the snapshot and other snapshots). This quality makes it possible to take a snapshot of a volume in practically zero time, regardless of its size. Redirect-on-write - The basic data duplication mechanism is redirect-on-write (rather than copy-on-write), dramatically reducing the impact of snapshots on system performance. The traditional copy-on-write approach involves three disk-seek operations, whereas the XIV system's redirect-on-write involves only two such operations. Inter-module copying - The IBM XIV system ensures that redirect-on-write is performed entirely within a module, with no intra-module communication. As a result, a huge bandwidth is put to the service of the redirect-on-write operation with no common bottleneck arising. In contrast, bottlenecks exist in traditional storage systems as they perform copy-on-write between disk shelves through a common controller, connected via FC. Concurrent copying in all modules - The redirect-on-write operation is performed on all modules concurrently and load-balanced perfectly by the IBM XIV system's scheme of spreading all volumes over all disks and modules. This provides huge power and full scalability to snapshot performance.
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