2.3 Alternate Data Backup Stream Structure

Some file systems support files that have named streams. The ALTERNATE_DATA dwStreamId field value MUST be used when recording these streams. Aside from the requirement that ALTERNATE_DATA MUST have a nonzero length name in the cStreamName field of the WIN32_STREAM_ID (section 2.2) structure, an ALTERNATE_DATA stream is identical to a DATA (section 2.4) stream. An underlying file system might constrain the naming of alternate streams. If the implementation does not support named streams or does not support the cStreamName that is specified in the ALTERNATE_DATA structure, the implementation MAY ignore the stream or MAY choose some other way to store the data.<2>