Cache writes fine, reads slowly


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Hello,

 

We are having difficulty figuring out why the reads to a share that should be only to our cache drives are starting off so quickly and then slowing down quite dramatically.

 

Attached is the diagnostic .zip. 

 

Basically, working with a 10 GB file, we can write to this cache (which is set to Only, which I take means that the share is only saved on the cache drive, for testing purposes). The upload gets very close to 1 GB/s. Immediately following this, the file is copied BACK off of the server (which should still be on cache) and it starts at about 1 GB/s but slows to nearly 250 MB/s at the halfway point in the transfer.

I've tried enabling write cache on all of the drives, and noticed that the first drive in our array is getting reads while this is happening. Is there a way to ensure that writes stay on the cache drive (which is a pool of 2 M.2 SSDs) until dumped into the array? 

 

This should not be put into the array so soon (several seconds) after writing to the cache drive.

 

 I hope that I've made clear what I would like to happen and the problems I am facing.

 

Thank you!

 

 

norunevillage-diagnostics-20200118-1056.zip

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I don't see a share named SuperFastTest.

 

There is a share anonymized as F------t. It is set to cache-yes and has files on cache and disk1. Possibly you wrote the test file to that share before setting it to cache-yes, so the file went to disk1, and any attempt to replace it or read it would be to the existing file on disk1.

 

There is another share anonymized as S------------e, could this be the one you mean? It is cache-only and has files only on cache.

 

See if you can clarify your description and perhaps repeat the test taking this information into account.

 

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