RAM cache (disk) support

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Hi all,


Since more hardwares support big memory now (64GB, 128GB or above), the feature of RAM cache (disk) becomes practical.

RAM cache has more i/o speed than SSD, and no worries about SSD lifetime. This feature can be either


  • Accelerating unraid JBOD arrays by RAM caching. Or,
  • User-defined temporary file storage


I would like to see this performance enhancement.



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On 3/6/2023 at 8:19 AM, itimpi said:

Any location that is not on a physical device would automatically be in RAM so you can get this already.


I apologize but could you elaborate on how to do this. I understand the basis of what you said however when I look to store data for example my Plex transcode folder in what I would like to be a Ram Cache. the only locations I can see would be the array or my unassigned drive (SSD) I am currently using. How would I point that to "Any location that is not a physical Device" If I can not see it? Sorry for such a noobish question. 

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On 3/11/2023 at 5:03 PM, JorgeB said:

Unraid has a default RAM disk on /dev/shm, it will use half installed RAM, and safer to use that.

Exactly. Many unix-style system has /dev/shm device that uses RAM first (could use swap file if needed) as "tmpFS".

That is what I need, but it is not convenient to use. Forgive me, in Unraid system, I don't really want to use the terminal.

So I request this feature to support RAM disk: maybe in a plugin, that could configure RAM disk on website, in cache pool or somewhere else.

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  • 4 months later...
  • 4 weeks later...

I have a (for me) huge amount of ram installed on my homeserver and tested creating dummyfiles on /dev/shm.

Unfortunatelly it seems that only half of the installed RAM is available. After a certain point i get "No space left on device." even though RAM is only half filled.


Is there a way to change that so that my RAM is not installed but unused all the time?

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On 8/30/2023 at 11:23 AM, nuhll said:


So, command in the go file it is?

sudo mount -o remount,size=XXXG /dev/shm



On 8/30/2023 at 11:23 AM, nuhll said:

I have all my dockers on dev shm and made it nearly full ram ("only" have 64gb)

Cool! Is there a guide how to do that?

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36 minutes ago, Greyberry said:


So, command in the go file it is?

sudo mount -o remount,size=XXXG /dev/shm



Cool! Is there a guide how to do that?

Wouldnt change it there. Install user scripts plugin and make a script run ONLY once at startup


A guide for what? Just change all directories (of temp files) which normally would go to appdata to dev shm.


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