An industry committee has recommended increasing the disk block sector size from 512 bytes to 4096. IDEMA, the International Disk Drive, Equipment, and Materials Association, says the 30-year standard of 512B should be increased eightfold to 4KB. It will mean disk drives can hold more data and hosts access it faster.
IDEMA Long Block Committee member Dr. Martin Hassner of Hitachi GST said: "(The) increasing areal density of newer magnetic hard disk drives requires a more robust error correction code (ECC), and this can be more efficiently applied to 4096 byte sector lengths." A Hitachi paper on the topic can be found here.
That is because, with the increasing areal density of disks, a bad area corrupts more bits. Having error-correction work over longer bit-strings makes more data recoverable.
The change means that only seven eighths (87.5 percent) of the number of sectors will be needed at any disk size. With longer sectors there will be fewer inter-sector gaps on a disk drive and less overhead in the form of sector headers and tails. Up to seven eighths of the non-data space on the disk will be recovered for data storage. Most file systems have a 4KB block size and most servers have a 4KB Memory page size. Reading file data will require one read for 4KB of data whereas eight reads are needed now. RAID systems will be able to spend more time on data work and less time on handling block sector overhead.
The IDEMA committee includes the major hard drive manufacturers plus electronics and server companies. Microsoft also participated and plans to include a 4KB sector capability in its forthcoming Windows Vista.
IDEMA foresees the first hard drive products becoming available later this year or in 2007. Backward compatibility with existing 512B products, both in hardware and in software, will be defined and accommodated during the phase over period. It is projected that most disk drives will be eventually formatted for 4KB sectors.
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