Understanding that snapshots are instantaneous copy images of volume data with the state of the data captured exactly as it appeared at the specific point in time that the snapshot was created, enabling users to save the volume data state and then access the specific volume data whenever needed, including after the source volume has changed.
Creating EMC XtremIO snapshots, which can be done at any time, does not affect system performance, and a snapshot can be taken either directly from a source volume or from other snapshots within a source volume’s group (Volume Snapshot Group).
The original copy of the data remains available without interruption, while the snapshot can be used to perform other functions on the data. Changes made to the snapshot’s source do not change or impact on the snapshot data.
XtremIO's snapshot technology is implemented by leveraging the content-aware capabilities of the system (Inline Data Reduction), optimized for SSD media, with a unique metadata tree structure that directs I/O to the right timestamp of the data. This allows efficient creation of snapshots that can sustain high performance, while maximizing the media endurance, both in terms of the ability to create multiple snapshots and the amount of I/O that a snapshot can support.
When creating a snapshot, the system generates a pointer to the ancestor metadata (of the actual data in the system). Therefore, creating a snapshot is a very quick operation that does not have any impact on the system and does not consume any capacity. Snapshot capacity consumption occurs only if a change requires writing a new unique block.
XtremIO snapshots are space-efficient both in terms of additional metadata consumed and physical capacity. Snapshots are implemented using a redirect-on-write methodology, where new writes to the source volume (or snapshot) are redirected to new locations, and only metadata is updated to point to the new data location. This method guarantees no performance degradation while snapshots are created.
Snapshots can be accessed like any other volume in the cluster in read write mode to enable a wide range of uses, including:
- Logical corruption protection — Taking frequent snapshots that are based on a defined recovery point objective (RPO) interval enables you to utilize snapshots for recovery of logical data corruption. The snapshots are saved in the system for as long as deemed necessary, and remain available for recovery use, should logical data corruption occur, thus enabling recovery of an earlier application state (prior to logical data corruption occurrence) to a known point in time prior to the corruption of the data.
- Backups — Presenting snapshots to a backup server (or agent) enables offloading the backup process from the production server.
- Development and testing — Taking snapshots of production data enables you to create multiple space-efficient, high-performance copies (snapshots) of the production system for the purpose of development and testing.
- Clones — Using persistent writable snapshots enables achieving clone-like capabilities. The snapshots can act as clones of the production volume to multiple servers. Clone performance is identical to that of the production volume.
- Offline processing — Use snapshots as a means of offloading data processing from the production server. For example, if you need to run a heavy process on data (which may be detrimental to the production server's performance), you can use snapshots to create a recent copy of the production data and then mount it on a different server. The process can then be run (on the other server), without consuming the production server's resources.
In summary, it is the highly efficient use of shared in-memory metadata that makes creating an EMC XtremIO snapshot a very quick operation, with no impact on production systems and without consuming any capacity. Snapshots can then be mounted to other servers to enable offline processing, such as analytics and reporting.
Further details can be found in the EMC XtremIO Storage Array User Guide, available at the EMC Support.
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