RAID

Answered Question
Aug 14th, 2007
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Dear All,


Can i get any document regarding RAID(Redundant array of independent disks)?


aman

Correct Answer by Rob Huffman about 9 years 11 months ago

Hi Aman,


Here is some info on RAID;


Here is a clip from Wikipedia;


RAID combines physical hard disks into a single logical unit either by using special hardware or software. Hardware solutions often are designed to present themselves to the attached system as a single hard drive and the operating system is unaware of the technical workings. Software solutions are typically implemented in the operating system, and again would present the RAID drive as a single drive to applications.


There are three key concepts in RAID: Mirroring, the copying of data to more than one disk; Striping, the splitting of data across more than one disk; and Error correction, where redundant data is stored to allow problems to be detected and possibly fixed (known as Fault tolerance). Different RAID levels use one or more of these techniques, depending on the system requirements. The main aims of using RAID are to improve reliability, important for protecting information that is critical to a business, for example a database of customer orders; or where speed is important, for example a system that delivers on-demand TV programs to many viewers.


The configuration affects reliability and performance in different ways. The problem with using more disks is that it is more likely that one will go wrong, but by using error checking the total system can be made more reliable by being able to survive and repair the failure. Basic mirroring can speed up reading data as a system can read different data from both the disks, but it may be slow for writing if it insists that both disks must confirm that the data is correctly written. Striping is often used for performance, where it allows sequences of data to be read off multiple disks at the same time. Error checking typically will slow the system down as data needs to be read from several places and compared. The design of RAID systems is therefore a compromise and understanding the requirements of a system is important. Modern Disk arrays typically provide the facility to select the appropriate RAID configuration.


RAID systems can be designed to keep working when there is failure - disks can be hot swapped and data recovered automatically while the system keeps running. Other systems have to be shut down while the data is recovered. RAID is often used in High availability systems, where it is important that the system keeps running as much of the time as possible.


From this link;


http://en.wikipedia.org/wiki/RAID



From Networkworld;


http://www.networkworld.com/details/728.html



The RAID Tutorial


http://www.ecs.umass.edu/ece/koren/architecture/Raid/raidhome.html



Hope this helps!

Rob

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Correct Answer
Rob Huffman Tue, 08/14/2007 - 04:47
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Hi Aman,


Here is some info on RAID;


Here is a clip from Wikipedia;


RAID combines physical hard disks into a single logical unit either by using special hardware or software. Hardware solutions often are designed to present themselves to the attached system as a single hard drive and the operating system is unaware of the technical workings. Software solutions are typically implemented in the operating system, and again would present the RAID drive as a single drive to applications.


There are three key concepts in RAID: Mirroring, the copying of data to more than one disk; Striping, the splitting of data across more than one disk; and Error correction, where redundant data is stored to allow problems to be detected and possibly fixed (known as Fault tolerance). Different RAID levels use one or more of these techniques, depending on the system requirements. The main aims of using RAID are to improve reliability, important for protecting information that is critical to a business, for example a database of customer orders; or where speed is important, for example a system that delivers on-demand TV programs to many viewers.


The configuration affects reliability and performance in different ways. The problem with using more disks is that it is more likely that one will go wrong, but by using error checking the total system can be made more reliable by being able to survive and repair the failure. Basic mirroring can speed up reading data as a system can read different data from both the disks, but it may be slow for writing if it insists that both disks must confirm that the data is correctly written. Striping is often used for performance, where it allows sequences of data to be read off multiple disks at the same time. Error checking typically will slow the system down as data needs to be read from several places and compared. The design of RAID systems is therefore a compromise and understanding the requirements of a system is important. Modern Disk arrays typically provide the facility to select the appropriate RAID configuration.


RAID systems can be designed to keep working when there is failure - disks can be hot swapped and data recovered automatically while the system keeps running. Other systems have to be shut down while the data is recovered. RAID is often used in High availability systems, where it is important that the system keeps running as much of the time as possible.


From this link;


http://en.wikipedia.org/wiki/RAID



From Networkworld;


http://www.networkworld.com/details/728.html



The RAID Tutorial


http://www.ecs.umass.edu/ece/koren/architecture/Raid/raidhome.html



Hope this helps!

Rob

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