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Erasure Coding post process

  • 18 March 2021
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From the Nutanix Bible: “when a Curator full scan runs, it will find eligible extent groups which are available to become encoded. Eligible extent groups must be "write-cold" meaning they haven't been written to for awhile”.

I have 2 questions:

if I have some data just written in the oplog, how long takes to copy those datas in the extent store, assuming that there is not any read of it?

Once the data are in the extent store, how long it takes before the erasure coding is applied to the datas?

 

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Best answer by Alona 19 March 2021, 05:34

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Alona
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Hi balma01,

As you can imagine, there is no set timeframe to write data between the two locations in the storage layer. Per-vDisk OpLog limit is 6GB. We can simplify it terribly and say, we are draining all 6GB (not realistic) for all vDisks at the same time (even less realistic), how long will it take?

In real life, it would be chunks of data written to the extent store from the OpLog if the vDisk is idle for some time or when the OpLog is at 85% capacity. Regular curator scans identify chunks that are old enough to be moved to the cold tier and to be processed for EC if it is enabled.

Cold data constitutes no write within the past 7 days. That is calculated from the moment the data arrives at the extent store.

Let me know if that helped or if you have more questions.

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