partition : Computer Hardware Buyers’ Glossary


Introduction Partition Layout
Types of Partitions My Layout
Playing with Partitions Links
Why Partitions?


A physical disk drive is usually broken into large chunks called partitions. The main advantage of this is avoiding putting all your eggs in one basket. If something goes wrong with a partition’s control tables, the other partitions are unaffected. With a smaller partition, it will be faster to find a file or directory since there is less data to wade through.

Each partition used by Windows gets assigned a drive letter, usually C:, D:, E: etc. You can put other operating systems, such an Ubuntu Linux, in other partitions.

Types of Partitions

Back in the days of DOS (Disk Operating System), allowing 4 partitions per disk seemed generous. Oddly that limit is still with us in the form of a maximum of 4 primary partitions per disk. If you need more, which you nearly always do, you designate one or more of your four primary partitions as an extended partition, then split it up into many subpartitions sometimes called secondary partitions or by old timers as logical volumes.

You must mark one of your four primary partitions as active. This means it’s operating system is the one that gets booted on power up. Partitions that contain a potentially bootable OS (Operating System) are marked bootable. Sometimes the boot invokes a tiny program called a boot manager that lets you dynamically choose which OS you want to boot. In theory you can’t boot a secondary partition, but in practice you can, by using a boot manager roosting in a primary partition that redirects to the secondary one.

Playing with Partitions

You can reassign drive letters and examine your partition structure in Control Panel ⇒ Administrative Tools ⇒ Computer Management ⇒ Disk Management. Windows comes with extremely primitive command line tools FDISK and DISKPART to manage partitions. Pretty well you have to decide when you first set up the machine what your partitions will be then leave the intact ever after. About the only thing you can do is convert a FAT32 partition to NTFS (New Technology File System).

However, with utilities like, Boot-It Bare Metal Acronis Disk Director or PartitionMagic you can create, delete, grow, shrink, shuffle, copy, split and merge partitions.

Since you can’t easily change a Windows partition while Windows is actively using it, you might find Linux partitioning utilities easier and safer to modify Windows partitions and Windows partitioning utilities easier and safer to modify Linux partitions.

Microsoft invented a proprietary partitioning scheme called dynamic disk that the partitioning utilities will not touch. Happily the home versions of  XP and Vista don’t support it, so you don’t have to worry about it if you are using a home edition.

Why Partitions?

When you buy a computer, usually it comes with only one giant C: Windows partition. Why would you want it otherwise?

One analogy is why would an icebreaker have containment cells? If an iceberg rips one open, the ship won’t sink. The others are still intact. With computers, if one partition is corrupted, the data on other partitions may still be fine. If Windows is in its own partition, when it becomes corrupt your data is still fine.

Another analogy is a house with only one giant room with all your stuff scattered all over. How would you find anything quickly when it could be anywhere? If you wanted to disinfect, you would have to disinfect the whole thing every time. You probably would not bother very often. With a computer, you might put your most active files in their own partition. You can the defrag that partition daily rapidly. If you moved files you rarely used to their own attic partition, the disk arms would not have to shuffle over them when looking for active files.

Windows is not the only operating system. If you reserve some partitions for Ubuntu/Linux, you can gradually move away from Windows.

Partition Layout

When you design your partitions, you want to reduce disk arm motion. This means keeping only a minimum amount of free space in each partition. If you had too much, the disk arms have to jump over the large free space band to get from partition to partition. You also want to keep your rarely used files off by themselves in the attic, and the end of the disk where the arms won’t often have to hop over them. Within a partition, you want to keep your files defragged and ordered so that the most frequently/recently used files are bunched together. Even with a tool like Boot-It Bare Metal, it is still a time consuming and risky business to expand the free space in a partition. You don’t want to do it more than twice a year. So you must leave sufficient free space for 6 month’s growth.

My Layout

On my Windows 7 machine I have 6 Windows partitions: Last revised/verified: 2014-07-03
Partition Use
C: boot, system Windows 7:64 bit
D: scratch
E: data files
F: Program Files
G: attic, purchased downloads, hot backups
H: attic, free downloads, hot backups. C: through G: are on SSD (Solid State Disk). H: is on a one terabyte hard disk
remainder The remainder of the disk for things like 32-bit Windows, Ubuntu, partition backups.
This scheme means if Windows dies and I have to do a clean re-install, I don’t lose my program files or data. I also keep rarely used files off by themselves at the end of the disc, saving head arm motion.

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