A format for providing platform interoperability and native OS support for CD-RW and DVD+RW disks. The "MRW" or "CD-MRW" format enables files to be saved to RW disks as if they were hard disks. Mount Rainier supports the UDF file system and automatically formats a blank disk when writing for the first time. Mount Rainier allows the disk to be ejected before being fully formatted by "de-icing" it, which saves the data necessary to continue the formatting later. See
UDF.
Mount Rainier also supports defect management, which masks bad sectors and writes the data into spares like a hard drive. In addition, it reduces block size from 64KB to 2KB for more efficient use of disk space. A driver can be added to legacy CD-ROM and CD-RW drives for read compatibility with MRW disks. See
CD-RW.