NT1230
Unit 2. Assignment 1 Disk Redundancy Research
1. What does RAID stand for? Redundant Array of Inexpensive Disk
2. When would we use RAID? When you have a vast amount of data to need to be backup or to improve speed of the system.
3. Define the following types of RAID:
a. RAID 0: Splits data evenly across two or more disks (striped) without parity information for speed. RAID 0 was not one of the original RAID levels and provides no data redundancy. RAID 0 is normally used to increase performance, although it can also be used as a way to create a large logical disk out of two or more physical ones.
b. RAID 1: An exact copy (or mirror) of a set of data on two disks. This is useful when read performance or reliability is more important than data storage capacity. Such an array can only be as big as the smallest member disk.
c. RAID 5: Comprises block-level striping with distributed parity. Unlike in RAID 4, parity information is distributed among the drives. It requires that all drives but one be present to operate. Upon failure of a single drive, subsequent reads can be calculated from the distributed parity such that no data is lost. RAID 5 requires at least three disks.
d. RAID 6: Extends RAID 5 by adding an additional parity block; thus it uses block-level striping with two parity blocks distributed across all member disks.
4. Why is RAID 0 of any use if it offers no redundancy? It splits data evenly across two or more disks (striped) without parity information for speed.
5. Why do you think that RAID 1 can be the most expensive? Why would people utilize it if it’s so costly? With this type of system, independent disk controllers are utilized, one for each drive, this is where the added expense comes in. The benefits that came with this expense are Multiplexing, Error Detection and Correction.
6. If you, as a home computer user, were to purchase a form of RAID, which would you choose and why? I would choose a RAID 1; I like the idea of having mirrored copies of my drive and the performance that duplexing give me in read performance.
7. What is the difference between software RAID and hardware RAID? Hardware is a physical controller that is attached to the drive, Software controller is a program were the host computer is responsible for the drives.
