RAID is used to either speed up drive performance and or to provide data redundancy. By placing data on multiple disks, I/O operations can overlap in a balanced way, improving performance. Since multiple disks increases the mean time between failure (MTBF), storing data redundantly also increases fault-tolerance.
A RAID appears to the operating system to be a single logical hard disk. RAID employs the technique of striping, which involves partitioning each drive's storage space into units which are interleaved and addressed in order.
In order to run RAID, you would have to have 2 or more identical Harddisk drives and a RAID controller card.
RAID-0 involves writing to 2 drives instead of one, thus cutting transfer times into half.
RAID-1 involves mirroring and consists of at least two drives that duplicate the storage of data.
Those are the 2 most common/popular forms of RAID-ing.
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-=S_Klass=- I tweak... therefore I am.
I'm not getting at you but just a slight correction ( I work on RAID systems for a living ). RAID increases the mean time between data related catastrophes not failures . If you have 4 drives with a MTBF of 100,000 hours then your actual MTBF is only 25,000 hours because each of the four drives can be expected to fail once in 100,000 hours. In 100,000 hours you are likely to have four failures - hence an MTBF of 25,000 hours.
No worries, the point is well taken, however since you brought it up, do clarify something for me. you said
Originally posted by Fishman:
If you have 4 drives with a MTBF of 100,000 hours then your actual MTBF is only 25,000 hours because each of the four drives can be expected to fail once in 100,000 hours.
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Now was that a MTBF of 100,000 hours on each drive or as the 4 drives together collectively? I would assume collectively from your next statements. And that's what I was referring to also. That, to put it simply, the chances of 2 or more drives all failing at the same time is far less then 1 drive failing at any one time.
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-=S_Klass=- I tweak... therefore I am.
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. If you have 4 drives with a MTBF of 100,000 hours then your actual MTBF is only 25,000 hours because each of the four drives can be expected to fail once in 100,000 hours. In 100,000 hours you are likely to have four failures - hence an MTBF of 25,000 hours.
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