What is RAID?
RAID stands for Redundant Array of Inexpensive Disks. Meaning that you can combine disks in different ways to create a large pool of space while protecting yourself from drive failures. Most RAID levels can survive the failure of at least one disk.
However, RAID is not a backup solution.
I'm going to say that again because it's important.
RAID is not a backup solution.
RAID only protects you from hardware failure. It doesn't save you from an errant rm -rf command. All the RAID in the world doesn't do you any good if all your files get deleted and you don't have backups somewhere else.
RAID 0 combines a minimum of two disks into a single large disk. Two 100gb disks would give you 200gb of usable space. You can use disks of different sizes but you're limited by the size of the smallest disk.
- Fast read/write speeds
- Lose one disk and you lose everything
RAID 1 mirrors the contents of one disk onto another disk. Two 100gb disks would give you 100gb of usable space.
- Easy to set up. Most controller cards support it and it's pretty fast as software RAID.
- Can easily handle a single drive failure and can sometimes handle multiple drive failures (depending on the total number of disks and the controller).
- While read speeds are normal, writes are twice as slow
- Not a very efficient use of available disk space.
RAID 5 spreads parity data across all disks giving you more available storage with a comparable fault tolerance to RAID 1. This is a flexible and cost-effective option.
- Makes good use of disk space. That means four 100gb drives would providing 300gb of usable space under RAID 5 while only providing 200gb of usable space under RAID 1.
- Very fast reads, medium-speed writes
- Requires a minimum of 3 drives.
- Rebuilding a failed array is much slower than RAID 1
- Controller cards are more expensive
RAID 10 - Mirroring & Striping
RAID 10 is a great option if cost and hardware are not an issue and is achieved by taking two RAID 1 arrays and combining them into a RAID 0 array. Four 100gb drives would yield 200gb of usable space.
- Fault tolerance of RAID 1
- Read/Write performance of RAID 0
- Expensive to implement. Controller cards are generally pretty expensive and also requires a minimum of four disks.
- Doesn't scale very well due to the sheer amount of hardware required.
Thanks to Wikipedia for the images. Don't worry, I'm not leeching them.