How to align partitions on an HDD with 4KB sectors

Some HDDs, like the Western Digital WD20EARS, use 4KB sectors rather than 512 byte sectors (it is called “Advanced Format”). If your partitions are misaligned, a read-modify-write performance penalty is incurred.

If you want to align your partition with 4KB HDD sectors, you should create a partition that starts from a sector divisible by 8 (Linux uses a 512-byte sector size, so 4096 bytes / 512 bytes = 8). So, very easy.

Example:

# parted /dev/sde
(parted) unit s
(parted) mkpart primary 2048 400TB
(parted) mkpart primary  781250560 -1
(parted) quit

Output for aligned HDD:

# parted /dev/sde unit s print
Model: ATA XXXXXXXXXX (scsi)
Disk /dev/sde: XXXXXXXXXXX
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start       End          Size         Type     
 1      2048s       781250559s   781248512s   primary 
 2      781250560s  1953525167s  1172274608s  primary

The parted --align=optimal option can be used too to select the optimal alignment, but disk parameters should be detected correctly to use this option with 4KB sectors.

Links:

• Advanced Format
• GNU Parted