Western Digital gears up for mighty formatting

Ten per cent space boost soon come

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WD and other disk drive manufacturers are increasing disk sector size eightfold to prepare for 2TB-plus capacity drives.

Current hard disk drives have a 512 byte data sector sector size and have had for up to 30 years. Each sector has a sync/DAM header and an ECC (error checking and control) trailer followed by an inter-sector gap. A 2TB drive will have, approximately, 3,906,250,000 sectors (3.9bn).

By enlarging the data sector to 4096 bytes, meaning 953,674 sectors in a 2TB drive, the drive will need eight times fewer sync/DAM headers, ECC blocks and inter-sector gaps. The ECC block will need to be around 50 per cent larger to cope with the extra data load.

Overall, Western Digital says, there will be a seven to 11 per cent increase in hard drive capacity. Even so, the sector count will get back up to 3.8bn when 8TB drives arrive, and go past that as capacities increase further, which will mean, apparently, another sector format scheme refresh.

WD is starting to ship 500GB Caviar Green drives with the new sector scheme. It says in a white paper (pdf) that its Advanced Formatting scheme has been optimised for Windows Vista and 7, and Mac OS X versions from Tiger onwards.

Other and maybe older operating systems can use the new Advanced Format drives but may well need to have changes applied to do so. A WD Align software facility can be downloaded to change the operating system so that partitions are aligned on 4096 byte sector boundaries.

There are several measures to note. For operating systems that can't apply the changes WD says each physical 4096 byte sector is presented as 8 logical 512 byte sectors by the hard disk drive interface. Specifically for Windows XP, an installation of an Advanced Format drive can involve running a jumper between pins 7 and 8 on the hard drive before installing the drive.

WD Align would be run if you needed to install more than one partition or under other circumstances. The utility will have to be run with either Vista or Windows 7 if you wish to have more than a single partition on the new drive.

A hard drive's firmware cannot be updated to apply the new sector scheme, as such sectorisation operates below the level of the firmware. ®

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