Fault Tolerance of Logical Drive(s) | ![]() |
For links and interfaces common to all Express Configuration links, please see Express Overview in ACU help. In the following screens, you will be asked a few simple questions that will allow you to set the RAID type for the logical drives on your controller. You will have a chance at the end to review your choices and make changes before they are saved. On this screen you will be asked what fault tolerance you would like. You have various RAID options: RAID 0 - No Fault
Tolerance However, because no logical drive capacity is used for redundant data, this method offers the best processing speed and capacity. You may consider assigning RAID 0 to drives that require large capacity and high speed, but pose no safety risk. RAID 1+0 - Drive Mirroring If a physical drive fails, the mirror drive provides a backup copy of the files and normal system operations are not interrupted. The mirroring feature requires a minimum of two drives and, in a multiple drive configuration (four or more drives), mirroring can withstand multiple simultaneous drive failures as long as the failed drives are not mirrored to each other. RAID 5 - Distributed Data Guarding RAID 5 requires an array with a minimum of 3 physical drives. The capacity of the logical drive used for fault tolerance depends on the number of physical drives in the array. For example, in an array containing 3 physical drives, 33 percent of the total logical drive storage capacity is used for parity data; a 14-drive configuration uses only 7 percent. RAID ADG -
Advanced Data Guarding RAID ADG read performance is similar to that of RAID 5, since all drives can service read operations, but the write performance is lower than that of RAID 5 because the parity data must be updated on multiple drives. Performance is reduced further in a degraded state. RAID ADG requires an array with a minimum of 2+P physical drives, where P is the number of drives used to store parity data; normally, P= 2. The percentage of the total drive capacity used for fault tolerance is equal to the number of drives used for parity data divided by the total number of physical drives. For example, in an array of five physical drives that has two parity drives, 40 percent of the total logical drive storage capacity is used for fault tolerance. A 14-drive configuration that also has two parity drives uses only 14 percent of storage capacity for fault tolerance. Note: Some controllers may not support this option. In this case, the Advanced Data Guarding (RAID ADG) option will not be available on this screen. RAID 4 - Data
Guarding RAID 4 requires a minimum of 3 physical drives (2 data drives and 1 parity drive) in an array. The capacity of the logical drive used for fault tolerance depends on the number of physical drives in the array. For example, in an array containing 3 physical drives, only 33 percent of the total logical drive storage capacity is used for fault tolerance; while a 14-drive configuration uses only 7 percent. Some new controllers or firmware versions may no longer support this option. In this case, the Data Guarding (RAID 4) option will not be available. |