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.