RAID (Redundant Array of Inexpensive/Independent Disks)

Level	Explanation	Advantages	Disadvantages	Remarks
0	Striping across disks	Larger I/Os or throughput Full utilization of disk array capacity Good for read & write	No fault tolerance One disk fails, entire volume fails. Cannot recover from failed disk.	Usually 2-4 drives. Applications requiring high performance but non –critical data and low cost.
1	Mirroring	Highest fault tolerance. Good for read	Higher cost	Smaller applciations with high availability
0 + 1	Striping + Mirroring	Very high reliability Good for read & write High performance	Higher cost	Samller applications with high performance
2	Inherently parallel mapping and protection technique. Mostly it is not deployed because it needs special disk futures. Disk production is not economical cost wise.
3	Data striped across disks. Min. 3 disks are required	Cost is lower than other redundant levels	Bottleneck for small I/O operations RAID 3 is not found on all controllers.	Large I/O request like CAD, CAM imaging.
4	Similar to Raid 3. Unlike Raid 3 it wirtes parity in a single disk.	Parity data for whole array requires just one disk.	Bottleneck for small I/O operations due to	Large file transfers
5	Calculates parity, and writes the data in stripes across disks. Rotational parity	Smaller datafiles high throughput. Even if one disk fails system will be up and runing. Reasonable cost.	Slower Write than Raid-3 and Raid-4. Write performance poor. Recovery is slow.	Very high read rate. Less write applications. OLTP File server Web server

ORACLE - RAID MATRIX

Oracle files	Raid Levels
Parameter files	5 , 0+1 , ANY
Control files	5, 0+1, ANY
Redo logs	1, 0+1
System Tablespace	5,1, 0+1
Temporary Tablespace	0
Rollback Tablespace	5
Data files	5 , 0+1
Index Tablespace	5, 0+1