RAID 10 Demystified

RAID 10, which is short for Redundant Array of Inexpensive (or Independent) Disks 10, is a feature you will see when comparing features of the various web hosts.

RAID is a method of providing greater storage and increased data reliability through redundancy. In effect, multiple disk drives are combined into a single logical unit and data is distributed across the combined units. The operating system sees the multiple disks as a single disk.

You may want to use RAID to:

  • increase speed
  • increase storage
  • back up data
  • a combination of some or all of the above.

The data can be distributed across the combined disks in several ways, known as RAID levels. The RAID levels are numbered from 0 to 6, and RAID 10 combines levels 1 and 0.

In RAID 1 data is stored as a mirrored set, with identical data written to multiple disks in an array. The mirroring guards against failures and disk errors, and as long as one of the sets is functioning the system continues to operate. The drawbacks are there is no increase in performance and the costs are greater.

In RAID 0 improves performance and provides additional storage but there is no redundancy or fault tolerance. Data written to RAID 0 disks is broken into blocks and alternate blocks are written to stripes on the same sector of each disk simultaneously. In other words, each disk (in a two-disk array) holds half the data with the first bit of data being written on the first disk, the second on the second, the third on the first disk, and so on. This vastly increases read/write speeds, but if one of your disks fails, you effectively lose all the data.

Combining RAID 1 and 0 gives a system of mirrored disks with stripes laid on top of the mirrored disks. This “mirrored stripes” system gives you the data security advantages of RAID 1 and the performance advantages of RAID 0.

RAID 10 has many advantages: it is considered to be fast, crash-proof, offers increased performance and is fully redundant, offering your data full back up security. Its disadvantage is that it uses a lot of disk space and has less capacity than some other versions of RAID.