ODX is supported through remote file servers if the
remote share is an NTFS volume, and if the server is running Windows Server 2012
(assuming the remote stack also supports offload operations).
ODX does not need to be performed on files encrypted
with Bitlocker or NTFS encryption (EFS), deduplicated files, compressed files,
resident files, sparse files, or files participating in TxF transactions.
NTFS does not support offload FSCTLs under these
conditions:
When performed on files encrypted
with Bitlocker or NTFS encryption (EFS)
When performed on files within a
volsnap snapshot
When performed on deduplicated
files, compressed files, resident files, sparse files, or files
participating in TxF transactions
If the desired file range is
unaligned to the logical sector size on the source device, or if the desired
file range is unaligned to the logical sector size on the destination
device. This follows the same semantics as a non-cached IO.
If the destination file is not
preallocated (SetEndOfFile and not SetAllocation) before FSCTL_OFFLOAD_WRITE
In processing offload read and offload write, NTFS
first calls CcCoherencyFlushAndPurgeCache to commit any modified
data in the system cache. This follows the same semantic as a non-cached IO.