April 24, 20188 yr Hi all. This question is a twist on "how big of a parity disk do I need?". I understand that my parity drive limits the density of the disks I can use for my data (i.e. a 6TB Parity disk limits any individual data disk to 6TB in density). However, my question is related to total data density. For example, if I have a 10TB parity drive, is there a limit to the total number of 10TB data disks? I imagine at some point the parity syndrome/calculations for all my data drives will exceed the capacity of the Parity drive.
April 24, 20188 yr Community Expert 1 hour ago, idlacrosseplayer said: is there a limit to the total number of 10TB data disks? The only limit is the number of data devices supported by the license you have, 28 for the Pro version, there's no parity calculation limit.
April 24, 20188 yr Keep in mind though, that as you increase the number of drives, your risk increases. When doing a parity reconstruction, every other drive is used to reconstruct the failed drive. The more drives you have, the more the risk that another drive will fail while rebuilding the first failed drive. The parity drive does NOT keep any of your data. If you lose a drive, it does the maths using ALL the other data drives plus the parity drive and solves for the missing bit. If you lose 2 drives and you only have 1 parity drive, the answer is no longer solvable, the missing bits could be 1's or 0's. Here is the full explanation. https://lime-technology.com/wiki/Parity Keeping up with drive health and being sure to replace drives at the first sign of failure is critical.
April 24, 20188 yr Author 49 minutes ago, jonathanm said: Keep in mind though, that as you increase the number of drives, your risk increases. When doing a parity reconstruction, every other drive is used to reconstruct the failed drive. The more drives you have, the more the risk that another drive will fail while rebuilding the first failed drive. The parity drive does NOT keep any of your data. If you lose a drive, it does the maths using ALL the other data drives plus the parity drive and solves for the missing bit. If you lose 2 drives and you only have 1 parity drive, the answer is no longer solvable, the missing bits could be 1's or 0's. Here is the full explanation. https://lime-technology.com/wiki/Parity Keeping up with drive health and being sure to replace drives at the first sign of failure is critical. Ahhh, that page is the answer. So the parity drive, as the name implies, only stores the calculation of all the drives parity on a bit by bit basis. Since all the drives will only have 10TByte, and a parity calculation's result is one bit, then no matter how many drives exist, the parity drive will never use more than 10TB. Got it; thanks.
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