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slow write with ssd cache drive...

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Hello,

 

I'm confused with this issue, :/

 

It seems when I move some files with gb size then It start to move at 110MB/s but in a few seconds these reduced to 35MB/s aprox.

 

I have set a split level 2 on a user share folder, set to yes on cache drive because I use an SSD drive.

 

anyone have experimented this issue before?, thank you.

 

I attached an image as an example.

unraid.png.ceaa11c588f18579087dca7d105f3199.png

  • Community Expert

The faster speed is probably due to network. You can max that out while the data gets cached in RAM. Then the slower speed makes me wonder if you are really writing to the cache drive as you intend.

  • Author
The faster speed is probably due to network. You can max that out while the data gets cached in RAM. Then the slower speed makes me wonder if you are really writing to the cache drive as you intend.

 

Hi trurl,

 

Well, if I try to copy those files manually to cache drive share directly then I get the same situation, so first this copy fast but then It slow to 30MB/s.

 

I have 3xTB drives for data and plus 1x3TB for parity, two of the data disk has 5gb free space and the other has 115gb free space.

 

Maybe this is the problem with free low space?

  • Community Expert

What's the SSD model?

 

Sometimes when cache is slower than expected,  re-formatting brings it to normal.

  • Author

Hi, johnnie.

 

What's the SSD model?

 

Sometimes when cache is slower than expected,  re-formatting brings it to normal.

 

It's a "Samsung 850 PRO 256 GB". So you suggest to re-formatting again the SSD?

  • Community Expert

It worked for me one time,  no clue why.

  • Author

I can't remember it, but how can I reformat the cache drive  with the same file system type again?, throught command-line?

  • Community Expert

Change fs to a different one,  e.g. reiser,  you'll be asked to format it when starting the array,  then change back to what you're using and format again  (naturally all cache data will be deleted )

  • Author
Change fs to a different one,  e.g. reiser,  you'll be asked to format it when starting the array,  then change back to what you're using and format again  (naturally all cache data will be deleted )

 

thanks for help me,

 

The problem still resides in it after re-formatting the cache drive, so after proving other methods to find the problem then finally I fixed that by using tercacopy as a default transfer file and now I get always about 70-110MB/s of tranfer rate to cache drive. I know windows 10 has updated recently with some updates and I think one or more of those updates were the source of the problem. :/

 

You can max that out while the data gets cached in RAM

 

You know how can I achieve this?, I can't find any other post to explain that.

 

thanks.

  • Community Expert

You can max that out while the data gets cached in RAM

 

You know how can I achieve this?, I can't find any other post to explain that.

 

thanks.

 

By default unraid use 20% free RAM for cache, you can increase this by using this command:

 

sysctl vm.dirty_ratio=99

 

Use any setting you like up to 99% (this is free RAM, not total RAM), setting won't survive a reboot, needs to be added to your go file if you want it always on.

 

Not recommended if you don’t have UPS.

 

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