Q1: What is RAID?
Q2: What are the different RAID levels offered by OIC?
Q3: Which RAID level should I use?


Q1: What is RAID?
Posted: 11/09/2004
Answer: RAID is an acronym for Redundant Array of Inexpensive (or Independent) Disks. A RAID array is a collection of drives which collectively act as a single storage system, which can tolerate the failure of a drive without losing data, and which can operate independently of each other.

Q2: What are the different RAID levels offered by OIC?
Posted: 11/09/2004
Answer: RAID Level 0: RAID Level 0 is not redundant, hence does not truly fit the “RAID” acronym. In Level 0, data is split across drives, resulting in higher data throughput. Since no redundant information is stored, performance is very good, but the failure of any disk in the array results in all data loss. This level is commonly referred to as striping.
RAID Level 1: RAID Level 1 is commonly referred to as mirroring with 2 hard drives. It provides redundancy by duplicating all data from one drive to another drive. The performance of a Level 1 array is slightly better than a single drive, but if either fails, no data is lost. This is a good entry-level redundant system, since only two drives are required. However, since one drive is used to store a duplicate of the data, the cost per megabyte is high.
RAID Level 5: This level is commonly referred to as striping with distributed parity. RAID Level 5 is similar to level 4, but distributes parity among the drives. No single disk is devoted to parity. This can speed small writes in multiprocessing systems. Because parity data must be distributed on each drive during reads, the performance for reads tends to be considerably lower than a level 4 array. The cost per megabyte is the same as for the level 4.

Q3: Which RAID level should I use?
Posted: 11/09/2004
Answer: The right choice depends on the application. The RAID Levels below provide a brief summary and general uses.
Level 0 (striping): Any application that requires very high-speed storage, but does not need redundancy. Photoshop temporary files are a good example.
Level 1 (mirroring): Applications that require redundancy with fast random writes; entry-level systems where only two drives are available. Small file servers are an example.
Level 5 (distributed parity): Similar to level 4, but may provide higher performance if most I/O is random and in small chunks. Database servers are an example.