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2010-03-10 12:31:14
By Mark Ward
technology correspondent, BBC News
Hard drives are about to undergo one of the biggest format shifts in 30 years.
By early 2011 all hard drives will use an "advanced format" that changes how
they go about saving the data people store on them.
The move to the advanced format will make it easier for hard drive makers to
produce bigger drives that use less power and are more reliable.
However, it might mean problems for Windows XP users who swap an old drive for
one using the changed format.
Error codes
Since the days of the venerable DOS operating system, the space on a hard drive
has been formatted into blocks 512 bytes in size.
The 512 byte sector became standardised thanks to IBM which used it on floppy
disks.
While 512 bytes was useful when hard drives were only a few megabytes in size,
it makes less sense when drives can hold a terabyte (1000 gigabytes), or more
of data.
"The technology has changed but that fundamental building block of formatting
has not," said David Burks, a product marketing manager for storage firm
Seagate.
This fine resolution on hard drives is causing a problem, he said, because of
the wasted space associated with each tiny block.
Each 512 byte sector has a marker showing where it begins and an area dedicated
to storing error correction codes. In addition a tiny gap has to be left
between each sector. In large drives this wasted space where data cannot be
stored can take up a significant proportion of the drive.
Moving to an advanced format of 4K sectors means about eight times less wasted
space but will allow drives to devote twice as much space per block to error
correction.
"You can get yourself into a corner where you cannot squeeze much more onto the
disk," said Steve Perkins, a technical consultant for Western Digital.
This shift also allows manufacturers to make more efficient use of the real
estate on a hard drive.
"We can put more data on the disk," he said. "It's about 7-11% more efficient
as a format."
Slow down
Through the International Disk Drive Equipment and Materials Association
(Idema) all hard drive makers have committed to adopting the 4K advanced format
by the end of January 2011.
Hard drive makers have begun an education and awareness campaign to let people
know about the advanced format and to warn about the problems it could inflict
on users of older operating systems such as Windows XP.
This is because Windows XP was released before the 4K format was decided upon.
"The 512 byte sector assumption is ensconced into a lot of the aspects of
computer architecture," said Mr Burks from Seagate.
By contrast, Windows 7, Vista, OS X Tiger, Leopard, Snow Leopard and versions
of the Linux kernel released after September 2009 are all 4K aware.
To help Windows XP cope, advanced format drives will be able to pretend they
still use sectors 512 bytes in size.
When reading data from a drive this emulation will go unnoticed. However, said
Mr Burks, in some situations writing data could hit performance.
In some cases the drive will take two steps to write data rather than one and
introduce a delay of about 5 milliseconds.
"All other things being equal you will have a noticeable hard drive reduction
in performance," said Mr Burks, adding that, in some circumstances, it could
make a drive 10% slower.
In a bid to limit the misalignment, hard drive makers are producing software
that ensures 512 sectors line up with 4K ones.
Those most likely to see the performance problems are those building their own
computers or swapping out an old drive for one that uses the new format.
Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/technology/8557144.stm
Published: 2010/03/09 11:29:38 GMT