DragonFly users List (threaded) for 2006-03
[OT] Disk sector size
I thought this quote was interesting. I'm wondering how much work will
be involved for you guys to accommodate this proposed change:
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."
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.