Advanced Format
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
Disk sector
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. Each sector stores a fixed amount of user data. Traditional formatting of these storage media provides space for 512 bytes or 2048 bytes of user-accessible data 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
Error detection and correction
In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels...

 algorithms to maintain data integrity at higher storage densities.


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. 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. 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. 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 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
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 and some operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

s as well as its correlation to the size of standard transactions in relational data base systems.
512-byte Emulated Device Sector Size
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 seven to eleven percent in physical platter space. 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.
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, 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 support 512e format drives with certain hotfixes installed (but not 4Kn), as do contemporary versions of Linux 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 system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

s, database engine
Database engine
A database engine is the underlying software component that a database management system uses to create, read, update and delete data from a database....

s, hard drive partitioning
Disk partitioning
Disk partitioning is the act of dividing a hard disk drive into multiple logical storage units referred to as partitions, to treat one physical disk drive as if it were multiple disks. Partitions are also termed "slices" for operating systems based on BSD, Solaris or GNU Hurd...

 and imaging
Disk image
A disk image is a single file or storage device containing the complete contents and structure representing a data storage medium or device, such as a hard drive, tape drive, floppy disk, CD/DVD/BD, or USB flash drive, although an image of an optical disc may be referred to as an optical disc image...

 tools, backup
In information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....

 and file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...

 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-byte 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-byte 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-byte sector onto the disk media. This operation, known as read-modify-write
In computer science, read-modify-write is a class of atomic operations such as test-and-set, fetch-and-add, and compare-and-swap which both read a memory location and write a new value into it simultaneously, either with a completely new value or some function of the previous value. These...

(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.
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 partial 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 make applications ready for the transition to Advanced Format technologies are being spearheaded by the Long Data Sector Committee and the hard disk drive manufacturers.

External links

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