here - OSTA - Optical Storage Technology Association
here - OSTA - Optical Storage Technology Association
here - OSTA - Optical Storage Technology Association
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2.2.13.1 Metadata File (and Metadata Mirror File)<br />
These files shall have the values of 250 (main) and 251 (Mirror) recorded in the IcbTag<br />
File Type fields of their File Entries. The UniqueID field of these File Entries shall have a<br />
value of zero.<br />
The Allocation Descriptors (see 2.3.10) of these files shall at all times:<br />
• Be SHORT_ADs (referencing space in the same physical/sparable partition in<br />
which the ICB resides).<br />
• Either be of type “allocated and recorded” or type “not allocated”.<br />
• Have an extent length that is an integer multiple of the Allocation Unit Size<br />
specified in the Metadata Partition Map.<br />
• Have a starting logical block number which is an integer multiple of the<br />
Alignment Unit Size specified in the Metadata Partition Map.<br />
The Information Length field of the File Entries for these files shall be equal to (number<br />
of blocks described by the ADs for this stream * logical block size).<br />
The Allocation Descriptors for this file shall describe only logical blocks which contain<br />
one of the below data types. No user data or other metadata may be referenced.<br />
• FSD<br />
• ICB<br />
• Extent of Allocation Descriptors (see 2.3.11).<br />
• Directory or stream directory data (i.e. FIDs)<br />
• An unused block marked free in the Metadata Bitmap File.<br />
NOTE: In the case w<strong>here</strong> the Duplicate Metadata Flag in the Metadata Partition Map is<br />
set, the allocations for the Metadata File and Metadata Mirror File should be as far apart<br />
(physically) as possible. Typically this is achieved by maximizing the difference between<br />
the start LBNs of the extents belonging to the file and its mirror. Likewise the file entries<br />
for these two files should be recorded as far apart as possible. Some drive/media<br />
combinations support “background physical formatting” (see 6.13 and 6.14) or<br />
“incremental formatting”, and implementations using such features should consider this<br />
when locating the metadata files and data. In such cases it may be practically impossible<br />
to position the files far apart without impacting the early eject time / media readability.<br />
The Access Time and Modification Time fields of the Metadata File and Mirror File File<br />
Entries shall be set to legal values at format time but need not be updated by a file system.<br />
The File Entries for the Metadata File and Metadata Mirror file shall have NULL<br />
Stream_Directory_ICB and Extended_Attribute_ICB fields.<br />
UDF 2.01<br />
43<br />
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