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.
Since the days of the venerable DOS operating system, the space on a hard drive has been formatted into blocks 512 bytes in size. 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.
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. This shift also allows manufacturers to make more efficient use of the real estate on a hard drive.
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. 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, 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, 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.
