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Advanced Format

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Advanced Format (AF)
Advanced Format 512e logo
Generation One Standard
4096 (4K) bytes-per-sector
Generation One Categories
512 emulation (512e)4K physical sectors on the drive media with 512 byte logical configuration
4K native (4Kn)4K physical sectors on the drive media and 4K configuration reported to the host.
4K-ready host[1]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 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 disk sector format used to store data on magnetic disks in hard disk drives (HDDs) that exceeds 512 to 520 bytes per sector, such as the 4096-byte (4 KB) sectors of the first-generation Advanced Format hard disk drives. Larger sectors use the storage surface area more efficiently for large files but less efficiently for smaller files, and enable the integration of stronger error correction algorithms to maintain data integrity at higher storage densities.

Advanced Format is also considered a milestone technology in the history of HDD storage, where data has been generally processed in 512-byte segments since at least the introduction of consumer-grade HDDs in the early 1980s, and in similar or smaller chunks in the professional field since the HDD's invention in 1956.

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 the conflict between continuing increases in data storage densities, known as areal density, and the traditional 512-byte-per-sector format used in hard disk drives.[2] Without revolutionary breakthroughs in magnetic recording system technologies, areal densities, and with them 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] In August 2005, Seagate shipped test drives with 1K physical sectors to test partners.[3] In 2010, industry standards for the first official generation of long data sectors using a configuration of 4096 bytes-per-sector, or 4K, were completed. The industry transition to 4K was designated as January 2011.[4] 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.

Overview

Generation-one Advanced Format, 4K sector technology, utilizes the storage surface media more efficiently by combining data that would have been stored in eight 512-byte sectors into one single sector that is 4096 bytes (4K) 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 database systems.[5]

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.[6] 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.[7]

Hard disk drive format efficiency with Advanced Format 4K technology and distributed ECC.

The Advanced Format standard employs the same gap, sync and address mark configuration as the traditional 512-byte sector layout, but combines eight 512 byte sectors into one data field.[8]

Having a huge number of legacy 512-byte sector-based hard disk drives shipped up to the middle of 2010, many systems, programs and applications accessing the hard disk drive are wrapped 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, Windows Server 2008, and Windows Server 2008 R2 support 512e format drives with certain hotfixes installed (but not 4Kn),[9] as do contemporary versions of FreeBSD[10][11][12] and Linux.[13][14] Mac OS X Tiger and onwards can use Advanced Format drives [15] and OS X Mountain Lion 10.8.2 additionally supports encrypting those. Windows 8 and Windows Server 2012 also support 4Kn Advanced Format.[9] Oracle Solaris 10 and 11 support 512e and 4Kn Advanced Format.[16]

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.

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 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.

Potential areas using 512-byte-based code.

The translation of the 4096-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 4096-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 4096-byte sector containing the targeted data into internal memory, integrate the new data into the previously existing data and then rewrite the entire 4096-byte 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 misaligned and a RMW performance penalty incurred.[17][18]

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.[19][20]

4K native

Advanced Format 4K native logo

For hard disk drives working in the 4K native mode, there is no emulation layer in place, and the disk media directly exposes its 4 KB physical sector size to the system firmware and operating system. That way, externally visible logical sectors organization of the 4K native drives is directly mapped to their internal physical sectors organization.

Readiness of the support for 4 KB logical sectors within operating systems differs among their types, vendors and versions.[13][21] Though, as of October 2013, there are still no 4K native hard drives available on the market, and all Advanced Format devices are utilizing the 512e emulation instead.[22]

The color version of the logo indicating a 4K native drive is similar to the 512e logo, but features four rounded corners, a blue background, and text "4Kn" at the center of the logo.[23]

References

  1. ^ "Advanced Format Definitions, Abbreviations, and Conventions". IDEMA. Retrieved March 13, 2012. {{cite web}}: External link in |publisher= (help)
  2. ^ a b "The Advent of Advanced Format". IDEMA. Retrieved 2013-11-18.
  3. ^ "The Transition to Advanced Format 4K Sector Hard Drives" (PDF). Seagate Technology. 2010. Retrieved March 13, 2012.
  4. ^ "Advanced Format – The Migration to 4K Sectors". Solution Center. Seagate Technology. Archived from the original on 19 May 2011. Retrieved June 27, 2011. {{cite web}}: External link in |work= (help); Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  5. ^ Smith, Ryan (December 18, 2009). "Western Digital's Advanced Format: The 4K Sector Transition Begins". AnandTech. Retrieved March 13, 2012.
  6. ^ Swinburne, Richard (April 1, 2010). "The Facts: 4K Advanced Format Hard Disks". bit-tech. Retrieved March 13, 2012. {{cite web}}: External link in |publisher= (help)
  7. ^ Hassner, Martin; Grochowski, Ed (May 31, 2005). 4K Byte-Sector HDD-Data Format Standard. Windows Hardware Engineering Conference. Retrieved March 13, 2012. {{cite conference}}: Cite has empty unknown parameter: |booktitle= (help); External link in |publisher= (help)
  8. ^ Curtis E. Stevens (2011). "Advanced Format in Legacy Infrastructures: More Transparent than Disruptive" (PDF). idema.org. Retrieved 2013-11-05.
  9. ^ a b "Advanced format (4K) disk compatibility update (Windows)". November 28, 2012. Retrieved January 3, 2013.
  10. ^ http://ivoras.net/blog/tree/2011-01-01.freebsd-on-4k-sector-drives.html
  11. ^ http://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html
  12. ^ http://www.wonkity.com/~wblock/docs/html/disksetup.html
  13. ^ a b Jonathan Corbet (2010-03-09). "4K-sector drives and Linux". LWN.net. Retrieved 2013-10-04.
  14. ^ Martin K. Petersen (2009-11-24). "Linux Storage Topology and Advanced Features" (PDF). Oracle Corporation. Retrieved 2013-10-04.
  15. ^ "How to install a WD Advanced Format Drive on a non-Windows Operating System". January 19, 2012. Retrieved April 12, 2013.
  16. ^ "Oracle Solaris 11.1 Administration: Devices and File Systems". Oracle Corporation.
  17. ^ Michael E. Fitzpatrick. "4K Sector Disk Drives: Transitioning to the Future with Advanced Format Technologies" (PDF). Toshiba. Retrieved 2013-10-24.
  18. ^ Goldwyn Rodrigues (2009-03-11). "Linux and 4K disk sectors". LWN.net. Retrieved 2013-10-24.
  19. ^ "Download the Hitachi Align Tool". Advanced Format Drives. Hitachi Global Storage Technologies. 2010. Archived from the original on 23 June 2011. Retrieved August 3, 2011. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  20. ^ "Advanced Format Software". Support. Western Digital. 2011. Retrieved January 6, 2012.
  21. ^ "Microsoft support policy for 4K sector hard drives in Windows". Microsoft. Retrieved 2013-10-24.
  22. ^ "Are there any drives that are 4k logical?". hardforum.com. July 2013. Retrieved 2013-10-23.
  23. ^ "Advanced Format Logo Overview". IDEMA. Retrieved 2014-01-10.
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