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

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