Home > Storage > PowerScale (Isilon) > Product Documentation > Data Efficiency > Dell PowerScale OneFS: Data Reduction and Storage Efficiency > Inode protection
Protection for inlined data operates the same way as for other inodes and involves mirroring. OneFS uses mirroring as protection for all metadata because it is simple and does not require the additional processing overhead of erasure coding. The number of inode mirrors is determined by the nodepool’s achieved protection policy, as in the following table:
OneFS protection level | Number of inode mirrors |
+1n | 2 inodes per file |
+2d:1n | 3 inodes per file |
+2n | 3 inodes per file |
+3d:1n | 4 inodes per file |
+3d:1n1d | 4 inodes per file |
+3n | 4 inodes per file |
+4d:1n | 5 inodes per file |
+4d:2n | 5 inodes per file |
+4n | 5 inodes per file |
Note: Unlike file inodes above, directory inodes, which comprise the OneFS single namespace, are mirrored at one level higher than the achieved protection policy. The root of the LIN Tree is the most critical metadata type and is always mirrored at 8x.