Similarity based data reduction, which complements VAST Cluster's data compression and deduplication mechanisms, is an optional feature that can save a lot of storage space when a lot of data is similar yet not identical. Similarity detects data blocks that are similar yet not identical and uses that similarity to store newly written data such that only the change between the older similar blocks are stored. The similar blocks are linked together in clusters. The reduction ratio may be further improved at a later time through re-clustering, in which similarity linkages between blocks are broken to allow new linkages between blocks of higher similarity.
Similarity-based data reduction is performed only on data that is written when similarity is enabled.
Similarity-based data reduction is enabled by default on newly installed clusters, although it is possible to install a cluster with similarity disabled. You can disable similarity at any time.
To disable similarity-based data reduction after installation at any time, connect to the VAST CLI and run the command
cluster modify --disable-similarity.
To enable similarity-based data reduction, run the VAST CLI command
cluster modify --enable-similarity.
In the VAST Web UI, open the Cluster tab of the Settings page. You can reach this by searching at the top left or from navigation menu on the left of the page.
In the Features section, slide the Enable similarity slider to the on or off position to enable or disable the feature.
Click Save to save your change.
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