A format for CD-RW and DVD+RW optical discs. Introduced by Microsoft in 1999, the "MRW" or "CD-MRW" format enables files to be stored like hard drives. Mount Rainier supports the UDF file system and automatically formats a blank disc when writing for the first time. Known as "de-icing," a disc can be ejected before being fully formatted and be finalized later. See
UDF.
Mount Rainier also supports defect management, which masks bad sectors and writes the data into spare sectors. In addition, it reduces block size from 64KB to 2KB for more efficient use of space. For older optical drives, a driver enables MRW read compatibility. See
CD-RW.