Short introduction to disks:

A "hard disk" is (classically - the logic is still used even if it doesn't look like that any more) a stack of rotating platters mounted on a common spindle. On these platters there are concentric rings ("tracks") of magnetic coating. These concentric rings are divided in "sectors".

As the spindle is rotating a device goes in between the platters which looks like a comb, carrying a read/write head on every tip.

The output now tells you the geometry of this disk - at least, as it is told by the disk device to the controller: it has 255 heads, meaning there are are 128 such platters. (Every platter has a lower and an upper side to read from and has 2 [read-write-] heads therefore.)

There are 6527 concentric tracks (=cylinders) on every disk. Because the corresponding tracks on all the platters build a logical unit it is easy to see why this is called a "cylinder".

Lastly, every such track is divided into 63 sectors. Note that sectors occupy a certain angle rather than a certain area of magnetic material. The inner sectors are therefore shorter than the outer sectors, but still can carry the same amount of data. This is the reason why every track is divided into the same number of sectors.


This is the disk device itself. "/dev/sda" means the whole disk, while "/dev/sda<n>" means "a certain partition number <n> on /dev/sda"

The partition table layout for the first disk. Probably this is a Linux system disk and Linux can't boot from LVM volumes. Therefore a single partition "/dev/sda1" to boot from, probably mounted at "/boot" and containing the boot loader (Grub?). Than a partition "/dev/sda2", which contains a swap partition. It is possible to have swap partitions inside the LVM, but some Linux admins hold that it is better to have the swap outside LVM too. Finally a LVM partition, which contains all the other volumes/filesystems there are in the system.



The second disk /dev/sdb. It seems not to carry any partitions at all yet. Similar for all the other disks in your system.

I hope this helps.

bakunin