To make the most efficient use of drive capacity, it is advisable to use drives of the same capacity. This is because the capacity of each drive is limited to the capacity of the smallest drive in the unit. Fault Tolerance:
| RAID Type | Description |
| RAID 5 | This type of unit provides performance, fault tolerance, and high storage efficiency. RAID 5 units can tolerate one drive failing before losing data. |
| RAID 6 | Provides very high fault tolerance with the ability to protect against two consecutive drive failures. Performance and efficiency increase with higher numbers of drives. |
Possible Configurations Based on Number of Drives.
| # Drives | Possible RAID Configurations |
| 3 | RAID 5 |
| 4 | RAID 5 |
| 5 or more | RAID 5RAID 6 |
The total array capacity is defined as follows: Drive Capacity
| RAID Level | Capacity |
| RAID 5 | (number of Drives – 1) x (capacity of smallest drive)Storage Efficiency Increases with the number of disks:Storage efficiency = (number of drives -1) / (number of drives) |
| RAID 6 | (number of drives -2) x (capacity of smallest drive) |
Example 1 3 2TB HDDs RAID 5 Capacity = (3-1) x 2 = 4TB RAID 6 Capacity = N/A requires 4 or higher total HDDs Example 2 4 2TB and 1 4TB HDDs RAID 5 Capacity = (5-1) x 2 = 8TB RAID 6 Capacity = (5-2) x 2 =6TB Auto-Carving Note: If the capacity of the unit you create will exceed 2TB and you are using Windows 2000, Windows XP, Linux 2.4, or FreeBSD 4.x, you will need to enable auto-carving.
Auto-carving divides the available arrays capacity into multiple chunks of 2 TB volumes that can be addressed by the operating systems as separate volumes. Then, when you boot to the operating system, each volume appears as a different disk drive.