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A OneFS powered cluster eliminates much of the overhead that traditional storage systems consume. By not having RAID groups, OneFS evenly distributes, or stripes, data among a cluster's nodes with layout algorithms that maximize storage efficiency and performance. The system continuously reallocates data across the cluster, further maximizing space efficiency. At the same time, OneFS protects data with forward error correction, or FEC—a highly efficient method of reliably protecting data.
You can view the protection levels in the WebUI by going to Data Management > Storage Pools > SmartPools and selecting the wanted node pool or tier. For example:
The hybrid protection schemes are particularly useful for PowerScale Gen6 chassis and other high-density node configurations, where the probability of multiple drives failing far surpasses that of an entire node failure.
For all current Gen6 hardware configurations, the recommended protection levels are ‘+2d:1n’ or ‘+3d:1n1d’.
In the unlikely event that multiple devices have simultaneously failed, such that the file is “beyond its protection level,” OneFS will re-protect everything possible and report errors on the affected individual files to the cluster’s logs.
OneFS also provides various mirroring options ranging from 2x to 8x, allowing from two to eight mirrors of the specified content. Metadata, for example, is mirrored at one level above FEC by default. For example, if a file is protected at +2n, its associated metadata object will be 4x mirrored.
The full range of OneFS protection levels are summarized in the following table:
Protection level | Description |
+1n | Tolerate failure of 1 drive OR 1 node (Not Recommended) |
+2d:1n | Tolerate failure of 2 drives OR 1 node |
+2n | Tolerate failure of 2 drives OR 2 nodes |
+3d:1n | Tolerate failure of 3 drives OR 1 node |
+3d:1n1d | Tolerate failure of 3 drives OR 1 node AND 1 drive |
+3n | Tolerate failure of 3 drives or 3 nodes |
+4d:1n | Tolerate failure of 4 drives or 1 node |
+4d:2n | Tolerate failure of 4 drives or 2 nodes |
+4n | Tolerate failure of 4 nodes |
2x to 8x | Mirrored over 2 to 8 nodes, depending on configuration |
See the OneFS Technical Overview white paper for further details on OneFS data protection levels.
OneFS enables the protection policy to be modified in real time, while clients are attached and reading and writing data. Be aware, however, that increasing a cluster’s protection level may increase the amount of space consumed by the data on the cluster.
OneFS also provides underprotection alerting for new cluster installations. If the cluster is underprotected, the cluster event logging system (CELOG) will generate alerts. The alerts warn the administrator of the protection deficiency and recommend a change to the appropriate protection level for that cluster’s configuration.