Overview
IEC 62842:2015 - Multimedia home server systems: File allocation system with minimized reallocation specifies a file-space allocation method for hard disk recorders (HDRs) that reduces file fragmentation and the need for costly reallocation (defragmentation). The standard applies this method to the Universal Disc Format (UDF) file system used on hard disk drives (HDDs) in multimedia home servers and recorders, targeting environments with continuous recording, deletion and updating of variable-length media files (e.g., time-shifted video and EPG data).
Key topics and technical requirements
- No-fragmentation allocation: The standard specifies how to allocate requested file space so that files are stored without fragmentation to minimize later reallocation.
- CoPo2 (Concatenation of power of 2): The basic allocation method defined in IEC 62842. CoPo2 uses power-of-two sized regions to simplify allocation and reduce fragmentation.
- Buddy allocation concept: Regions are recursively divided into equal power-of-two “buddies” until the smallest containing region is allocated for a request.
- Partition strategies: Guidance on applying CoPo2 to existing partitions or to virtual container partitions that contain power-of-two allocation units.
- Management tables and data structures: Rules for region configuration master tables, multilevel-divided-partition allocation tables, and space bitmap descriptors to track allocation state.
- Required functions: Specification of functional operations such as Initialize and Manage-multilevel-divided-partitions needed to implement CoPo2.
- UDF integration: Details on how to apply CoPo2 management tables and data structures within UDF volume and partition descriptors (including use of ImplementationUse fields).
Applications and who should use it
- Device manufacturers and firmware developers building hard disk recorders, DVRs, and multimedia home servers who need robust, low-fragmentation storage for continuous recording workloads.
- System integrators and embedded software engineers implementing or optimizing UDF file systems on HDDs for consumer electronics.
- Product architects looking to improve recording performance and reduce downtime by minimizing the need for full-system defragmentation.
- Test labs and standards compliance teams verifying allocation behavior against IEC 62842 requirements.
Benefits
- Improved sustained write/read performance for time-shift and continuous-recording applications.
- Reduced service windows and user disruption compared with traditional defragmentation.
- Predictable allocation behavior using power-of-two regions and explicit management tables.
Related standards
- ISO/IEC 13346 and OSTA UDF specifications (referenced in IEC 62842) for UDF volume and file structures.
- UDF and optical/Blu-ray related standards when integrating with BD library functions (noting IEC 62842 also references Blu-ray recorder considerations).
Keywords: IEC 62842:2015, multimedia home server systems, file allocation, minimized reallocation, CoPo2, UDF, hard disk recorders, HDD, buddy allocation, fragmentation.