All approved UDF 2.60 DCNs

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All approved UDF 2.60 DCNs 6.x.1 Characteristics of Media formatted for Pseudo OverWrite Media formatted for Pseudo OverWrite will support multi-track recording. All logical sectors in the volume space on the media can be overwritten. The file system can write concurrently to multiple tracks. A track is defined as reserved or used, see 1.3.2. Each track is sequentially recordable only. The Next Writable Address (or NWA) is obtained by the file system by querying the drive and points to the next recordable logical sector within the track. In addition to sequential recording, any logical sector in a track before the NWA can be independently overwritten. Also sectors in a used track (having no valid NWA) can be overwritten. Overwriting is supported by the drive by recording updated data either within the Spare Area (by the linear replacement algorithm) or to some NWA within the volume space. UDF does not currently propose any policy specifiable by the file system to control physical placement of data being overwritten. While performing sequential recording on the medium after requesting the NWA of a track, the drive system shall behave in such a way that the NWA will not change unexpectedly, or without notification, until the UDF implementation queries for the NWA of that track again. When pseudo overwrite is performed all the NWAs become invalid. The drive is entirely responsible for maintaining the remap entry information for the logical sectors that can and may be persisted within the volume space. 6.x.2 Write Strategy Tracks can be utilized to record different data types in a logically contiguous manner (e.g. metadata, metadata mirror and data, can be recorded in separate tracks). When all unrecorded sectors in a reserved track have been exhausted, the UDF implementation can assign a new reserved track (by splitting any existing reserved track) of an appropriate size. By allowing reserved tracks to be split, the drive enables recording of the AVDP (comprising volume structure) at any two locations of: LSN 256, the last LSN in the volume, or (Last LSN – 256) as per ECMA 167. It is desirable for UDF implementations to duplicate the metadata in the Metadata Mirror File. All approved UDF 2.60 DCNs 32 February 28, 2005
All approved UDF 2.60 DCNs Figure 1 below illustrates the track layout for a freshly formatted medium where the Metadata Mirror File is not being recorded. Track #1 contains the volume structure (including the AVDP at LSN 256) as well as related file structures. The Duplicate Metadata Flag in the Metadata Partition Map is set to zero. The format utility has allocated an extent (track) for metadata recording while Track #3 comprises the majority of recordable volume space to be utilized as required. Track #1 (used) Track #2 (reserved) Track #3 (reserved) Track #4 (used) Spare Area Volume Structure Metadata File FE Metadata Mirror File FE File Set Descriptor File Entry (root directory) unrecorded area unrecorded area AVDP Spare Area Metadata File extent Volume Space Figure 1: Freshly formatted medium – no Metadata Mirror File Figure 2 below also illustrates the track layout for a freshly formatted medium where the Metadata Mirror File will be recorded. The Duplicate Metadata Flag in the Metadata Partition Map is set to one. Hence an extent has been allocated for the contents of the Metadata Mirror File. Track #1 (used) Track #2 (reserved) Track #3 (reserved) Track #4 (reserved) Track #5 (used ) Spare Area Volume Structure Metadata File FE Metadata Mirror File FE File Set Descriptor File Entry (root directory) unrecorded area unrecorded area File Set Descriptor File Entry (root directory) unrecorded area AVDP . . Spare Area Metadata File extent Volume Space Metadata Mirror File extent Figure 2: Freshly formatted medium – Metadata Mirror File will be recorded All approved UDF 2.60 DCNs 33 February 28, 2005
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All approved UDF 2.60 DCNs

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