6.12. Realtime Allocator Limitations

In practice, the realtime allocator is not widely used.

It effectively uses a single large allocation group with a single set of data structures losing the parallelism of XFS’s allocation groups

The locks associated with this central data structure result in the serialisation of concurrent operations to a realtime device

The realtime allocator is incapable of maintaining a spatial separation on disk for concurrent operations

It tries to start new files at random points in the bitmap to reduce this problem but this has a negative impact on some workloads