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Computer Science/Parity in RAID level 5
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Hi we have been learning about the different levels of RAID in information technology recently. There is one thing that i am really struggling to get my head around and that is the parity in RAID level 5. How does it work? Is it as large as the rest of the files put together and if so why does it take up the same amount of disk space?
Caity:
Resource:
http://publib.boulder.ibm.com/infocenter/eserver/v1r2/index.jsp?topic=/diricinfo...
Understanding RAID level-5
RAID level-5 stripes data and parity across all drives in the array.
RAID level-5 offers both data protection and increased throughput. When you assign RAID level-5 to an array, the capacity of the array is reduced by the capacity of one drive (for data-parity storage). RAID level-5 gives you higher capacity than RAID level-1, but RAID level-1 offers better performance.
RAID level-5 requires a minimum of three drives and, depending upon the level of firmware and the stripe-unit size, supports a maximum of 8 or 16 drives.
The following illustration is an example of a RAID level-5 logical drive.
The data is striped across the drives, creating blocks.
Notice that the storage of the data parity (denoted by *) also is striped, and it shifts from drive to drive.
A parity block ( *) contains a representation of the data from the other blocks in the same stripe. For example, the parity block in the first stripe contains data representation of blocks 1 and 2.
If a physical drive fails in the array, the data from the failed physical drive is reconstructed onto the hot-spare drive.
Kind Regards,
Jeff
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Jeff Laatsch
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