Limitations with delayed allocation for extending writes feature

In the cases where the file data must be written to disk immediately, delayed allocation is disabled on that file. Examples of such cases include Direct I/O, concurrent I/O, FDD/ODM access, and synchronous I/O.

Delayed allocation is not supported on memory mapped files.

Delayed allocation is not supported with BSD quotas. When BSD quotas are enabled on a file system, delayed allocation is turned off automatically for that file system.

Delayed allocation is not supported for shared mounts in a cluster file system.