Advanced Format
 Advanced Format Logo | |
| Generation One Standard | |
|---|---|
| 4,096 (4K) bytes-per-sector | |
| Generation One Categories | |
| 512 emulation (512e): 4K physical sectors on the drive media with 512 byte logical configuration translation to the host. 4K native (4Kn): 4K physical sectors on the drive media and 4K configuration reported to the host. | |
| Year standard completed | |
| March 2010 | |
| Created by | |
| IDEMA Long Data Sector Committee, composed of Dell, Fujitsu (now Toshiba Storage Products Company), Hewlett-Packard, Hitachi Global Storage Technologies, IDEMA, LSI Corporation, Maxtor (now Seagate), Microsoft, Phoenix Technologies, Samsung, Seagate Technology, Western Digital | |
Advanced Format is a generic term pertaining to any sector format used to store data on the magnetic disks in hard disk drives that exceeds 512 to 520 bytes per sector. Advanced Format is also considered a milestone technology in the history of hard-drive storage, where data has been processed in 512-byte increments since the inception of the hard-disk drive in 1956. Changing the sector format convention to larger data sectors, such as the 4,096-byte structure used in the first generation of Advanced Format technologies, uses the storage surface area more efficiently for large files but less efficiently for smaller files, while enabling the integration of stronger error correction algorithms to maintain data integrity at higher storage densities.
History
The need for long data sectors was first identified in 1998 when a technical paper issued by the National Storage Industry Consortium (NSIC) called attention to dichotomies between continuing increases in data storage densities, known as areal density, and the traditional 512 byte per sector format used in hard disk drives.[1] Without revolutionary breakthroughs in magnetic recording system technologies, areal densities and with it, the storage capacities on hard disk drives were projected to stagnate.
The storage industry trade organization, International Disk Drive Equipment and Materials Association (IDEMA), responded by organizing the IDEMA Long Data Sector Committee in 2000, where IDEMA and leading hardware and software suppliers collaborated on the definition and development of standards governing long data sectors, including methods by which compatibility with legacy computing components would be supported.[2] Ten years later, industry standards for the first official generation of long data sectors using a configuration of 4,096 bytes-per-sector, or 4K, were completed. The industry transition to 4K was designated as January 2011.[3] Advanced Format was coined to cover what was expected to become several generations of long data sector technologies, and the Advanced Format logo was created to distinguish long data sector-based hard disk drives from those using legacy 512 to 520-byte sectors.
Advanced Format
Generation one categories:
- 512 emulation (512e): 4K physical sectors on the drive media with 512 byte logical configuration translation to the host.
- 4K native (4Kn): 4K physical sectors on the drive media and 4K configuration reported to the host.
- 4K-ready Host (Client devices only): A host system which works equally well with legacy 512 as well as 512e hard disk drives.
Advanced Format overview
Generation one Advanced Format, 4K sector technology, utilizes the storage surface media more efficiently by combining eight 512-byte sectors into one single sector that is 4096-bytes in length. Key design elements of the traditional 512-byte sector architecture are maintained, specifically, the identification and synchronization marks at the beginning and the error correction coding (ECC) area at the end of the sector. Between the sector header and ECC areas, eight 512 byte sectors are combined, eliminating the need for redundant header areas between each individual chunk of 512-byte data. The Long Data Sector Committee selected the 4K block length for the first generation AF standard for several reasons, including its correspondence to the paging size used by processors and some operating systems as well as its correlation to the size of standard transactions in relational data base systems.[citation needed]
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| Physical Sector 1 | Physical Sector 2 | ||||||||||||||
Format efficiency gains resulting from the 4K sector structure range from five to thirteen percent.[citation needed] The 4K format provides enough space to expand the ECC field from 50 to 100 bytes to accommodate new ECC algorithms. The enhanced ECC coverage improves the ability to detect and correct processed data errors beyond the 50 byte defect length associated with the 512-byte sector legacy format.[citation needed]
The Advanced Format standard employs the same gap, synch and address mark configuration as the traditional 512-byte sector layout, but combines eight, 512 byte sectors into one data field.
With an estimated 5.8 billion legacy 512-byte sector-based hard disk drives shipped since 1956 to the middle of 2010,[citation needed] many systems, programs and applications accessing the hard disk drive are configured around the 512 byte-per-sector convention. Early engagement with the Long Data Sector Committee provided the opportunity for component and software suppliers to prepare for the transition to Advanced Format. For example, Windows Vista, Windows 7 and Windows Server 2008 generally support Advanced Format, as do contemporary versions of Linux[citation needed] and Mac OS X Snow Leopard.
Direct Disk access operations, which will be influenced by Advanced Format, are used in all hard drive read and write operations.
Advanced Format categories
Among the Advanced Format initiatives undertaken by the Long Data Sector Committee, methods to maintain backward compatibility with legacy computing solutions were also addressed. For this purpose, several categories of Advanced Format devices were created.
Advanced Format 512e
Many host computer hardware and software components assume the hard drive is configured around 512-byte sector boundaries. This includes a broad range of items including chipsets, operating systems, database engines, hard drive partitioning and imaging tools, backup and file system utilities as well as a small fraction of other software applications. In order to maintain compatibility with legacy computing components, many hard disk drive suppliers will support Advanced Format technologies on the recording media coupled with 512-byte conversion firmware. Hard drives configured with 4096-byte physical sectors with 512-byte firmware are referred to as Advanced Format 512e, or 512 emulation drives.
The translation of the 4,096 physical format to a virtual 512-byte increment is transparent to the entity accessing the hard disk drive. Read and write commands are issued to Advanced Format drives in the same format as legacy drives. However, during the read process, the Advanced Format hard drive loads the entire 4,096 sector containing the requested 512-byte data into memory located on the drive. The emulation firmware extracts and re-formats the specific data into a 512-byte chunk before sending the data to the host. The entire process typically occurs with little or no degradation in performance.
The translation process is more complicated when writing data that is either not a multiple of 4K or not aligned to a 4K boundary. In these instances, the hard drive must read the entire 4,096-byte sector containing the targeted data into internal memory, integrate the new data into the previously existing data and then rewrite the entire 4,096 sector onto the disk media. This operation, known as read-modify-write (RMW), can require additional revolution of the magnetic disks, resulting in a perceptible performance impact to the system user. Performance analysis conducted by IDEMA and the hard drive vendors indicates that approximately five to ten percent of all write operations in a typical business PC user environment may be mis-aligned and a RMW performance penalty incurred.[citation needed]
When using Advanced Format drives with legacy operating systems, it is important to realign the disk drive using software provided by the hard disk manufacturer. Disk realignment is necessary to avoid a performance degrading condition known as cluster straddling where a shifted partition causes filesystem clusters to span multiple physical disk sectors. Since cluster to sector alignment is determined when creating hard drive partitions, the realignment software is used "after" partitioning the disk. This can help reduce the number of unaligned writes generated by the computing ecosystem. Further activities to ready applications for the transition to Advanced Format technologies are being spearheaded by the Long Data Sector Committee and the hard disk drive manufacturers.[citation needed]
References
- ^ "The Advent of Advanced Format". IDEMA. Retrieved 6 July 2011.
- ^ "The Advent of Advanced Format". IDEMA. Retrieved 6 July 2011.
- ^ "Advanced Format-The Migration to 4K Sectors". Seagate Technology. Retrieved 27 June 2011.
- ^ a b IDEMA and Toshiba, DISKCON Conference, September 2008.
- ^ Western Digital, December 2005
- ^ a b Seagate Technologies, “The Transition to Advanced Format Hard Drives”, 2010.