Advanced Format

Advanced Format (AF)
	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.; ; 4K-ready Host (Client devices only): A host system which works equally well with legacy 512 as well as 512e hard disk drives.
Year standard completed
	March 2010
Created by
	IDEMA Long Data Sector Committee, composed of Dell, Fujitsu (now Toshiba Storage Products Company), Hewlett Packard, Hitachi Data Storage Technologies, IDEMA, LSI Corporation, Maxtor (now Seagate) Microsoft Corporation, Phoenix Technologies, Samsung, Seagate Technology, Western Digital
	v; t; e;

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, utilizes the storage surface area more efficiently 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 NSIC^[vague] 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.^{[citation needed]} 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.^{[citation needed]} 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.^{[citation needed]} 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]}

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 ranges between five to thirteen percent.^{[citation needed]} The 4K format also provides enough space to increase the ECC field from 50 to 100 bytes to accommodate more powerful ECC algorithms. The enhanced ECC coverage boosts the ability to both detect and correct errors in the data being processed by the hard disk drive beyond the 50 byte defect length associated with the legacy 512-byte sector format.^{[citation needed]}

_{Figure 2. Hard disk drive format efficiency with Advanced Format 4K technology and distributed ECC}

_{Source: IDEMA and Toshiba, DISKCON Conference, September 2008}

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 and the Mac OS X Snow Leopard.

File:Afdiag2.jpg

_{Source: IDEMA Long Data Sector Committee}

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. 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 4,096-byte physical sectors with 512-byte firmware are referred to as Advanced Format 512e, or 512 emulation drives.

_{Figure 3. Potential areas using 512-byte based code}

_{Source: Western Digital, December 2005}

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 by 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 occurs with little or no degradation in performance.

_{Figure 4. Potential Advanced Format 512e read sequence}

File:Afdiag4.jpg

_{Source: Seagate Technologies, “The Transition to Advanced Format Hard Drives”, 2010}

The translation process is more complicated when the host system issues a write command to record data on the drive and the data is either not a multiple of 4,096 or not aligned to a 4,096 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 (or RMW), can require additional revolution(s) 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]}

_{Figure 5. Potential Advanced Format 512e write sequence}

File:Afdiag5.jpg

_{Source: Seagate Technologies, “The Transition to Advanced Format Hard Drives”, 2010}

Proper alignment of applications and utilities interfacing with the hard disk drive can reduce performance concerns with Advanced Format-based drives.^{[citation needed]} Since alignment is determined when creating hard drive partitions, tools that partition the drive to the proper alignment scheme used by the host operating system on client PCs have been developed. 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]}

External links