Partition X does not end on cylinder boundary

While reviewing the partion layout on one of my hard drives, I noticed a number of “Partition X does not end on cylinder boundary” messages in the fdisk output:

$ fdisk /dev/sda
Command (m for help): p

Disk /dev/sda: 80.0 GB, 80000000000 bytes
255 heads, 63 sectors/track, 9726 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xac42ac42

Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 204800 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 26 287 2097152 83 Linux
Partition 2 does not end on cylinder boundary.
/dev/sda3 287 9726 75822111+ 8e Linux LVM

This was a bit disconcerting at first, but after a few minutes of thinking it dawned on me that modern systems use LBA (Logical Block Addressing) instead of CHS (Cylinder/Head/Sector) to address disk drives. If we view the partition table using sectors instead of cylinders:

$ sfdisk -uS -l /dev/sda
Disk /dev/sda: 9726 cylinders, 255 heads, 63 sectors/track
Units = sectors of 512 bytes, counting from 0

Device Boot Start End #sectors Id System
/dev/sda1 * 63 409662 409600 83 Linux
/dev/sda2 409663 4603966 4194304 83 Linux
/dev/sda3 4603967 156248189 151644223 8e Linux LVM
/dev/sda4 0 - 0 0 Empty

We can see that we end at a specific sector number, and start the next partition at that number plus one. I must say that I have grown quite fond of sfdisk and parted, and they sure make digging through DOS and GPT labels super easy.

http://prefetch.net/blog/index.php/2009/09/12/why-partition-x-does-now-e...

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