Although hard drive capacities have been increasing by an average of 44% each year, according to industry figures, it has become clear that maintaining this rate of increase has become increasingly difficult because of the technological challenges and rapidly approaching physical limits of storing electrons onto magnetic media. To meet these challenges, hard disk drive manufacturers have developed a new way to squeeze an estimated 5-13% more out of a hard drive’s surface by changing the way hard disk platters are formatted.
When the first hard drive, IBM’s RAMAC, was introduced in 1956, a sector size of 512 bytes was defined. A sector corresponds to a few degrees on the surface of the hard disk – you can probably visualize this like a slice of pie. The platter is defined as a series of tracks – small, concentric circles that radiate out from the center of the disk. Rather than being a whole piece of pie, a sector is the small, radial piece that sits on one of the tracks.
The original 512 byte sector contains addressing information (so that a controller can locate the specific sector on a specific track), plus 512 bytes (or less) of data, and error correction code (ECC). The sector, designed to hold 512 bytes of data may have less, if there are fewer than 512 bytes of data to put onto the sector.
Although some hard disk drives and other storage devices also produced devices with 1024 byte sectors, the largest such change – a move to a 4096 byte sector – is currently under way. Seagate, Toshiba and Western Digital are now producing drives with 4096 byte sectors. This sector size – 8 times as large as the original 512 byte sector – delivers benefits to the drive makers and to the organizations or individuals using the new 4096 sector drives.
The first benefit to the manufacturer is the ability to increase the amount of data that can be stored on the drives by using some of the space that would otherwise have gone between each of the 512 byte sectors for data storage. Additionally, part of the recovered space is used for a larger error correction code. This more capable ECC field can use more powerful error correction algorithms, which could improve error detection and correction on sectors with problems.
These improvements don’t come without requiring a bit of modification to make the drives work when connected to computers that are designed to work with hard disk drives using 512-byte sectors. In order to accommodate virtually every current computer, new format specifications have been developed. Advanced Format 512e (or 512 emulated) is handled by the controller on the hard drive. This controller translates the 4096 byte sector into 512 byte ‘sectors’ that are sent to the computer or device sending or reading data. The work of translation is performed in the drive, and is transparent to the computer.
Read speeds may actually be better than those from a standard drive with 512 byte sectors because the entire 4096 byte sector’s contents are buffered in the hard drive controller for transfer to the attached computer. Writing times may be slightly slower, because the conversion of 512 byte data coming from the computer into 4096 bytes of data for writing to the sector may take longer than one disk rotation, causing a delay before writing.
Unlike many drive capacity changes that have occurred in the past –that required updating of drive controllers, updating of computer firmware, updating of operating systems, and other somewhat painful upgrades, the move to 4096 byte sectors should be transparent to users. What may become more obvious will be a continuing increases in hard drive size (due, in part, to the sector changes), perhaps fewer read failures (resulting from stronger error correction codes), and perhaps even slight read performance improvements.
[ed. – Aleratec hard drive duplicators support 4096 sector hard drives!]