Raid 10

RAID 10
Provides very high performance and redundancy. Datais simultaneously mirrored and striped. Can under circumstancessupport multiple drive failures.


Advantages
Highly fault tolerant
High data availability
Very good read / write performance
Disadvantages
Very expensive
Drive spindles must be synchronised
Not very scaleable

Applications
Where high performance and redundancy are critical

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Raid 0+1

RAID 0+1
Provides redundancy by writing all data to four or more drives.RAID 0+1 combines the benefits of RAID level 0 and RAID level 1.This offers both striping and mirroring with no parity generation.The RAID 0+1 also provides high performance and resilience to RAID 5.


Advantages
No parity generation
Easy to implement
Utilises full disk capacity
4 drives minimum
Higher performance than RAID 5
Disadvantages
Inefficient use of disk space
High disk overhead / Expensive
Costly to deploy

Applications
General File servers
Imaging applications
Medium size database applications

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Raid 5

RAID 5
Provides redundancy by writing data and parity informationacross three or more drives, thus increasing performance. The RAID Level 5provides the best combination of disk array technology. The mostpopular RAID level supplied.


Advantages
Most flexible of all disk arrays
Best balance cost / performance / protection of any RAID system
Allows multiple simultaneous writes
High read data rate
Medium write data rate
3 drives minimum
Ideal for small write applications
Highly efficient
Disadvantages
Inefficient with large file transfer
Disk failure has an impact on performance

Applications
Transaction processing
Relational Databases
File & Print Servers
WWW, E-mail, and News servers
Intranet Servers

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Raid 3

RAID 3
Provides redundancy by writing all data to three or moredrives. This RAID 3 disk array provides excellent storage for videoimaging, streaming, publishing applications or any system that requireslarge file block transfers.


Advantages
Single dedicated parity disk
High read data rate
High write data rate
4 drives minimum
No performance degradation if drive fails
Best and worst case performance similar
Disadvantages
Inefficient with small file transfer

Applications
Video Streaming
Video Publishing
Video Editing
Pre Press
Image editing
Any application that needs heavy updating and large file usage

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RAID 1
Provides redundancy by writing all data to two or more drives.The performance of a level 1 array tends to be faster on reads andslower on writes compared to a single drive, but if either drive fails,no data is lost. This is a good entry-level redundant system, since onlytwo drives are required; however, since one drive is used to store aduplicate of the data, the cost per megabyte is high. This level iscommonly referred to as mirroring.


Advantages
No parity generation
Easy to implement
Extremely fault tolerant
Utilises full disk capacity
2 drives minimum
Disadvantages
Inefficient use of disk space
High disk overhead
Doubles number of writes

Applications
Pre-Press
Video editing and production
Image manipulation/editing

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Raid 0

Top Raid 0 Raid 1 Raid 3 Raid 5 Raid 10 Raid 0+1


RAID 0
Offers no redundancy or fault tolerance, hence does not truly fit the"RAID" acronym. In level 0, data is striped across drives,resulting in higher data throughput. Since no redundant information isstored, performance is very good, but the failure of any disk in thearray results in data loss. This level is commonly referred to asstriping.


Advantages
No parity generation
Easy to implement
Cost effective
Utilises full disk capacity
Disadvantages
Not a true RAID
No redundancy / fault tolerance
Drive failure will result in data loss
Not suitable in mission critical environments

Applications
Pre-Press
Video editing and production
Image manipulation/editing


Dual controller Raid 0 offers better performance than a single controller

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Raid Levels

Raid Explained
RAID stands for Redundant Arrayof Inexpensive (or sometimes "Independent") Disks. RAID isa method of combining multiple hard disks in a single logical unit tooffer high availability, performance or a combination of both. Thisprovides better resilience and performance than a single disk drive.

The benefits of RAID explained

Provides real-time data recovery with uninterrupted access when a hard drive fails
Increases system uptime and network availability
Protects against data loss
Multiple drives working in parallel increases system performance
Software RAID

Many operating systems provide functionality for implementing software based RAID systems. Thesoftware RAID systems generate the RAID algorithms using the server CPU,this can severely limit the RAID performance. Should a server failthe whole RAID system is lost. Cheap to implement and only need asingle SCSI controller.

Hardware RAID

All RAID algorithms are generated on the RAID controller board, thus freeing the server CPU. Allows fullbenefits and data protection of RAID. More robust and fault tolerantthan software RAID. Requires dedicated RAID controller to work.

RAID levels

Various RAID levels exist these are 0, 1, 2, 3, 4, 5, 6, 7, 10, & 0+1. The levels of RAID protectionvaries with the RAID level selected RAID levels 0 & 1 are nottechnically RAID as they have no redundancy in the event of drivefailure. The most common RAID levels are shown below. RAIDlevels 2, 4, 6, 7 & 0+1 are a combination of the other RAID levelsshown.

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