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What is "RAID" concept ? Why it is needed ? How many types are there ?

Posted on 2007-12-05
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Hi,

I want to know "RAID" concept. Can you please explain me in SIMPLE terms :

1. What it is ?
2. Why it is needed ?
3. How many types are there ?

with plain english to understand basics easily.

Appreciate your time and patience !!

Thanks
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Question by:kishore_peddi
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by:
imitchie earned 672 total points
ID: 20416673
1. What it is ?
It is a way to use multiple DISKS working together as ONE storage system.

2. Why it is needed ?
For redundancy, better performance or both.

3. How many types are there ?
RAID 0, 1, 2,5,5, 10, 50,80,0+1 etc.

Here's a link to read more about it
http://en.wikipedia.org/wiki/RAID
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by:FilipZahradnik
FilipZahradnik earned 664 total points
ID: 20416695
RAID technology allows you to use multiple physical harddisks as one logical drive.

There are 2 main reasons why people do this:
- To improve reliability. This is done by having the same data stored on more than one physical disk so that when one disk fails, you still have your data on the other disk.
- To improve performance. This is done by spreading data accross multiple disks and reading/writing to those disks simmultaneously.

There are other more obscure reasons, but redundancy and performance are the main ones.

RAID configurations are described as RAID levels using a number, e.g. RAID0, RAID1, RAID5, etc. Each configuration has different properties and serves a different purpose. Then there are nested RAID levels, where you combine 2 levels, e.g. RAID1+0 (sometimes referd to as RAID10), RAID5+0, etc.

You can read more about RAID and RAID levels here: http://en.wikipedia.org/wiki/RAID
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Expert Comment

by:Wizilling
ID: 20417068
This would help
http://en.wikipedia.org/wiki/RAID

the most common ones are RAID 0, raid 10 , RAID 5
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Expert Comment

by:Yveau
ID: 20422987
On the different types, In a nutshell, best performance in OLTP database systems is RAID 10 ... but that is a pretty expensive as well ... for OLAP 5 turns out to be very good as well ...

and I'm not going to post the link for the fourth time :-)

Hope this helps ...
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by:dportas
dportas earned 664 total points
ID: 20429964
Everything you need to know about RAID5: www.baarf.com
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