ZFS ARC Cache

[vonkraus]

Question about ARC Cache for the ZFS pool...  Is there a way to allocate an nvme m.2 2tb drive to be used as the ARC Cache for my ZFS pool?   I have 32gb of RAM, installed awaiting an upgrade to ship that will put me at 64gb.  The problem I'm seeing is if I move a bunch of folders/files from one share to another regardless of method, the ZFS ram will fluctuate and climb during the process.  After the process is complete the ZFS RAM usage still stays at the max % used and doesn't fall off. 

 

If there's away; how?  

 

I've set my arc cache to 17179869184for 16GB to prevent maxing it out.  I've had a couple of scenario's where Overall processor load and all cpu cores have been maxed out to the point of UI lockup and a hard power cycle was the only way out.

 

Thanks in advance!

 

 

tower1-diagnostics-20231219-1434.zip

Edited December 19, 2023 by vonkraus

[MAM59]

The view is a bit misleading.

The zfs column shows only the total arc cache, so 54% of your 16Gb are in use currently.

Nothing to panic if it goes up to 100%, it even is supposed to go there.

 

And yes, it will stay there too as long as no new data is not coming in. Then it will free out the oldest stuff and give room to the newcomers. perfectly ok.

 

the RAM column is where you have to watch. If it goes up high there is really a problem you should take care off.

 

[vonkraus]

Ok thank you for clarifying.

 

On the other topic, is there a way to assign a nvme drive to be the arc cache for the zfs pool?  

[JorgeB]

For now only manually:

 

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/?do=findComment&comment=1256329

 

[vonkraus]

Thank you!