Chapter 4. Redundant Array of Independent Disks (RAID)

Chapter 4. Redundant Array of Independent Disks (RAID)

4.1. What is RAID?
4.2. Who Should Use RAID?
4.3. Hardware RAID versus Software RAID
4.3.1. Hardware RAID
4.3.2. Software RAID
4.4. RAID Levels and Linear Support
4.5. Configuring Software RAID
4.5.1. Creating the RAID Partitions
4.5.2. Creating the RAID Devices and Mount Points

The basic idea behind RAID is to combine multiple small, inexpensive disk drives into an array to accomplish performance or redundancy goals not attainable with one large and expensive drive. This array of drives appears to the computer as a single logical storage unit or drive.


[1] A hot-swap chassis allows you to remove a hard drive without having to power-down your system.

[2] RAID level 1 comes at a high cost because you write the same information to all of the disks in the array, which wastes drive space. For example, if you have RAID level 1 set up so that your root (/) partition exists on two 40G drives, you have 80G total but are only able to access 40G of that 80G. The other 40G acts like a mirror of the first 40G.

[3] Parity information is calculated based on the contents of the rest of the member disks in the array. This information can then be used to reconstruct data when one disk in the array fails. The reconstructed data can then be used to satisfy I/O requests to the failed disk before it is replaced and to repopulate the failed disk after it has been replaced.

[4] RAID level 4 takes up the same amount of space as RAID level 5, but level 5 has more advantages. For this reason, level 4 is not supported.


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