What is Advanced Format: 4K Sector Drives

I have a lot of friends that are becoming more and more aware of what is going on in the computing world.  As this development matures, I am confronted with more and more questions about the state of technology.  Sometimes, I can very easily explain the idea behind things, but the actual workings of it are somewhat foreign.  Recently, a friend of mine started building his own home server (WHS) and purchased a bunch of hard drives.  This normally wouldn’t be cause for concern, but the website he was purchasing from delineated these drives as 4K Sector drives.  So… what does that mean?

Traditional drives used technology that limited each sector of the drive to 512 bytes which has been the standard for nearly 30 years.  The 512 byte sector comprises a few basic components:

1. Sync/DAM (lead-in)
2. Inter-sector gaps
3. ECC (Error Correction Code) blocks

Maintaining the multiple blocks of ECC has proven to require a lot of overhead and reducing the number of these per sector can improve the efficiency of the drive.

With Advanced Format technology, it is possible to remove Sync/DAM blocks, inter-sector gaps, and 8 blocks of ECC.

The same amount of physical space now requires fewer ECC blocks, fewer lead-ins, and fewer gaps allowing for more continual data space and a larger ECC code word increasing data integrity.

Compatibility

Many devices cannot take advantage of the new disk technology including legacy operating systems like Windows XP.  To combat these limitations, the drives support a 512 byte emulation whereas each 4k physical sector is composed of eight 512 byte logical sectors.

Windows XP systems will need additional software to be able to use these drives with some additional limitations and requirements

The Benefits

With Advanced Format Technology an increase of format efficiency of 87% from the 512 byte sectors has been improved to a format efficiency of 96%.  The format efficiency gains can allow for an 11% increase in usable disk space while improving the error correction burst rate by 50%.