4K SECTORS

Advanced Format 4K native logoHistorically hard disks used 512 byte sectors. Early hard disks had very few sectors on a track so it was considered a good compromise at the time.

Over time, however, disk capacity grew exponentially to the point where the number of sectors on a track became unwieldy.

Seagate and WDC both adopted the move to 4096 bytes sector size which was still small enough not to be a problem with large numbers of small files. The industry called the new 4096 byte sectors the Advanced Format.

The advantage of using the larger sector size was to be able to use more robust error correcting codes. A 512 byte sector can typically correct a defect of up to 50 bytes in length. Today’s hard drives are beginning to push the limits on error correction with leading areal densities. Consequently, the migration to larger sectors within the hard drive industry has become a fundamental need relative to gaining improvements in error correction while also gaining additional capacity.

The larger 4K format has a larger 100 byte block size. This affords a much needed improvement in error correction. At the same time the improved tracks gain almost 10% in additional storage.

The industry change is needed. Older hard disks often show errors when the older ECC cannot cope with multiple bad blocks. Windows can map out bad allocation units to prevent use. The 4096 byte disks are much less likely to show bad sectors.

Hard disks shipped after June 2011 now generally are 4096 sector with 512 byte emulation. Checking the date code on the label. Disks may use year and week system so look for weeks above 30.

With larger capacity disks the move to 4096 byte sectors makes perfect sense. In 2016, Seagate offered 10 TB hard disks to consumers. Samsung offered 16TB SSD to servers. Seagate then announced 60TB SSD for servers. Now that Windows 10 has a large market share we expect that native 4K type disks will become available to consumers. For now hard disks are using an emulation layer but we expect that disks with switchable modes will become standard for many years.

Windows XP, Vista and 7 are designed for 512 byte sectors so hard disks have to emulate the legacy format using a translation table. Windows 8 and above are able to use the new 4096 byte disks in native mode which is not emulating the legacy 512 byte mode.