Partitions, Extended Partitions, and Logical Drives
Basic and dynamic hard disks have different properties in terms of partitions, extended partitions and logical drives. That’s why we have to learn the definitions to have a better understanding of the hard disk configurations.
Partitions are separate data areas that exist in a hard disk’s storage space. Suppose that you have one physical hard disk of 500 GB capacity. Further suppose that you want to divide this disk to 100 GB + 200 GB + 200 GB data areas. Each data area is called a partition.
Each partition can either be a primary partition or an extended partition. A primary partition contains only one file system. In Windows, this is the first partition and labeled as C:. An extended partition is a partition that contains secondary partitions. Following our example above, you can make a 100 GB primary partition and a 400 GB extended partition. With our explanation, the 100 GB primary partition has to have only one file system. Under the current Windows technology, this is NT File system (NTFS). You can divide the remaining 400 GB into separate partitions with different sizes, such as 200 GB, 100 GB and 100 GB.
For a partition to become a volume, it has to be formatted with a file system. Again following our example, if we format the 200 GB partition with NT file system, the 100 GB with FAT 32 and the remaining with ext2, then we have 3 logical volumes. The volumes are logical because they are not physical disks, they are formatted partitions (volumes) present on one physical disk.
Basic and Dynamic Disks
Basic and dynamic disks differ in terms of primary and extended partitions as well as with the logical volumes they can handle, such as:
- A basic disk can handle four partitions; either four primary or three primary and one extended. There is no other choice. However, the extended partition can handle up to 128 logical volumes.
- A dynamic disk can handle about 2000 volumes.
In addition, the partitions on a basic disk cannot split or share data with other partitions; each partition is an isolated separate space. On the other hand, you can do following arrangements (which are actually RAID configurations) on dynamic volumes, given that the volumes are formatted with NT file system (NTFS):
- Disk spanning: Combine an arbitrary number of disk volumes with arbitrary sizes into a single volume. For example, suppose that you have 15 GB free space in a partition on one physical disk, 10 GB free space in a partition on another physical disk and 5 GB free space in yet another disk. You can combine the 15 GB + 10 GB + 5 GB to make one volume of 30 GB.
- Disk striping: This is actually a RAID 0 configuration where you split data to be written among several hard disks. The minimum requirement is 2 hard disks, preferably identical both in make/model and size.
- Disk mirroring: This is a RAID 1 configuration where the data is identically written to at least 2 physical hard disks.
- RAID 5 (data striping with parity): In this configuration, the data is written to three disks and an additional parity value is also saved. You need at least 3 physical hard disks for this configuration.