http://cephnotes.ksperis.com/blog/2014/01/21/feature-set-mismatch-error-on-ceph-kernel-client
rbd_default_features
Description
The default features enabled when creating an block device image. This setting only applies to format 2 images. The settings are:
- 1: Layering support. Layering enables you to use cloning.
- 2: Striping v2 support. Striping spreads data across multiple objects. Striping helps with parallelism for sequential read/write workloads.
- 4: Exclusive locking support. When enabled, it requires a client to get a lock on an object before making a write.
- 8: Object map support. Block devices are thin provisioned—meaning, they only store data that actually exists. Object map support helps track which objects actually exist (have data stored on a drive). Enabling object map support speeds up I/O operations for cloning, or importing and exporting a sparsely populated image.
- 16: Fast-diff support. Fast-diff support depends on object map support and exclusive lock support. It adds another property to the object map, which makes it much faster to generate diffs between snapshots of an image, and the actual data usage of a snapshot much faster.
- 32: Deep-flatten support. Deep-flatten makes rbd flatten work on all the snapshots of an image, in addition to the image itself. Without it, snapshots of an image will still rely on the parent, so the parent will not be delete-able until the snapshots are deleted. Deep-flatten makes a parent independent of its clones, even if they have snapshots.
The enabled features are the sum of the numeric settings.
Type : Integer
Default : 3, or layering support and striping support.
