Home > Storage > PowerScale (Isilon) > Product Documentation > Storage (general) > Dell PowerScale: Considerations and Best Practices for Large Clusters > Maintaining appropriate protection levels
Ensure your cluster and pools are protected at the appropriate level. Every time you add nodes, re-evaluate protection levels. OneFS includes a ‘suggested protection’ function that calculates a recommended protection level based on cluster configuration, and alerts you if the cluster falls below this suggested level.
OneFS supports several protection schemes. These include the ubiquitous +2d:1n, which protects against two drive failures or one node failure, and +3d:1n1d, which guards against three drives or one node plus one drive failures.
The best practice is to use the recommended protection level for a particular cluster configuration. This recommended level of protection is clearly marked as ‘suggested’ in the OneFS WebUI storage pools configuration pages and is typically configured by default. For all current PowerScale hardware configurations, the recommended protection levels are either ‘+2d:1n’ or +3d:1n1d’.