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space consumed by raid6
How much overhead does raid6 add? If I had 300GB of data, how much
overhead would be added by the raid6 implementation? Does this also depend on how much data I have? Will the overhead change if I had more than 300GB, say 600GB? B |
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space consumed by raid6
On May 29, 5:07 pm, wrote:
How much overhead does raid6 add? If I had 300GB of data, how much overhead would be added by the raid6 implementation? Does this also depend on how much data I have? Will the overhead change if I had more than 300GB, say 600GB? The most common definitions of RAID6 (which is not all that well standardized) implies the equivalent of two disks in the array being dedicated to redundancy. In short, if you had a five disk array, you'd get three disks worth of usable storage out of them (66% overhead). If you had a 32 disk array, you'd get 30 disks worth of storage (6.6% overhead). So if you needed a RAID6 array with a capacity of 300GB, you might have five 100GB drives, or 32 10GB drives. If you needed 600GB of capacity, you might either do a 5x200GB array, a 8x100GB array, or what the heck, a 62x10GB array. The proper choice depends on cost and performance considerations. Of the last three configurations, the 5x200GB array will likely cost by far the least, but will perform by far the worst. The 62x10GB array will be very expensive, but very fast. Of course RAID6 for 300-600GB of storage is pretty silly (assuming current disk drives)... |
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space consumed by raid6
wrote in message
ups.com... The proper choice depends on cost and performance considerations. Of the last three configurations, the 5x200GB array will likely cost by far the least, but will perform by far the worst. The 62x10GB array will be very expensive, but very fast. Of course RAID6 for 300-600GB of storage is pretty silly (assuming current disk drives)... The speed of the RAID6 set will also depend on the capabilities of your controller. Most are designed to perform best with a certain number of disks. Very large number of disks (such as your example of 60 + 2) will most likely take some time on the controller to calculate parity in multiple steps, where it may be able to do this in a single step with 6+2... Rob |
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space consumed by raid6
On May 30, 12:33 am, "Rob Turk" wrote:
The speed of the RAID6 set will also depend on the capabilities of your controller. Most are designed to perform best with a certain number of disks. Very large number of disks (such as your example of 60 + 2) will most likely take some time on the controller to calculate parity in multiple steps, where it may be able to do this in a single step with 6+2... Regardless of the number of disks in the array, a RAID6 write (without any of the replaced data cached), will require three reads and three writes. OTOH, the required Galois field multiplication to compute the second parity block is painful without special hardware. |
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space consumed by raid6
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