Advanced Format

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The Advanced Format is a generic term pertaining to any disk sector format used to store data on magnetic disks in hard disk drives (HDDs) that uses 4 kilobyte sectors instead of the traditional 512 byte sectors. The main idea behind using 4096-byte sectors is to increase the bit density on each track by reducing the number of gaps which hold Sync/DAM and ECC (Error Correction Code) information between data sectors. The old format gave a format efficiency of 88.7%, whereas Advanced Format results in a format efficiency of 97.3%.

How to determine if HDD employ a 4k sector

The physical and logical sector size of hard disk /dev/sdX can be determined by reading the following sysfs entries:

$ cat /sys/class/block/sdX/queue/physical_block_size
$ cat /sys/class/block/sdX/queue/logical_block_size

Tools which will report the physical sector of a drive (provided the drive will report it correctly) includes

  • smartmontools (since 5.41 ; smartmontools -a, in information section)
  • hdparm (since 9.12 ; hdparm -I, in configuration section)

Note that both works even for USB-attached discs (if the USB bridge supports SAT aka SCSI/ATA Translation, ANSI INCITS 431-2007).

See also