Well that didn't add up...
Btw, RAID 5 and RAID 0+1 are completely different. I suppose I'll throw in my RAID-post again:
Here is "What You Need To Know About RAID".
RAID - Redundant Array of Independant Disks.
There are several types of RAID. Here are the most important.
Code:
RAID 0 - Stripe:
======================
Disk 1 Disk 2
------ ------
| 1 | | 2 |
| 3 | | 4 |
| 5 | | 6 |
| 7 | | 8 |
| 9 | | 10 |
| 11 | | 12 |
| 13 | | 14 |
| 15 | | 16 |
------ ------
RAID 1 - Mirror:
======================
Disk 1 Disk 2
------ ------
| 1 | | 1 |
| 2 | | 2 |
| 3 | | 3 |
| 4 | | 4 |
| 5 | | 5 |
| 6 | | 6 |
| 7 | | 7 |
| 8 | | 8 |
------ ------
RAID 3 (unusual):
======================
P = Parity information
Disk 1 Disk 2 Disk 3
------ ------ ------
| 1 | | 2 | | P |
| 3 | | 4 | | P |
| 5 | | 6 | | P |
| 7 | | 8 | | P |
| 9 | | 10 | | P |
| 11 | | 12 | | P |
| 13 | | 14 | | P |
| 15 | | 16 | | P |
------ ------ ------
RAID 5:
======================
P = Parity information
Disk 1 Disk 2 Disk 3
------ ------ ------
| P | | 1 | | 2 |
| 3 | | P | | 4 |
| 5 | | 6 | | P |
| P | | 7 | | 8 |
| 9 | | P | | 10 |
| 11 | | 12 | | P |
| P | | 13 | | 14 |
| 15 | | P | | 16 |
------ ------ ------
RAID 0: Striping. Two disks where the data is spread across the disks so that every second block is on one of the disks.
+ Improves speed.
- Unsafe.
RAID 1: Mirroring. Both disks contain the same data.
+ Safe.
- Wastes half the space.
RAID 3: A third drive stored parity information (XOR). If one disk dies, the data can be rebuilt using this information. One disk is the parity disk. Can be used for more than 3 disks as well.
+ Safe.
- Requires complicated controller.
RAID 5: Every n:th block in an array of n disks is a parity block. If one disk dies data can be saved. Can be used for more than 3 drives.
+ Safe.
- Requires complicated controller.
RAID configurations can sometimes be combined if the controller alows it. For example, RAID 50, RAID 10 and so on. RAID 50 requires at least 6 drives.
All RAID configurations require the disks to be of the same size. If they are not the size of the array is based on the size of the smallest drive.
If you don't have drives with the same size and want to run them as JBOD (Just a Bunch Of Disks). A bit like RAID 0 except it's not faster than a single drive.