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I have a pool of 5 x enterprise 12Gps SSD that I use for internal storage for a proxmox server. This pool is used to stand up VMs and containers. The problem is that it is eating up a lot of my available RAM which is 192G! Here is the summary: enter image description here

As you can see the Max size is 94.4GiB!!!

My question is: What should be the optimal value for this? and how to change it?

This is my production server and I want to be 100% sure of the process. (I already looked here but my server is also not honouring the arc size :( )

Any help or suggestions would be highly appreciated!

Shery
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  • *I already looked here but my server is also not honouring the arc size :(* Try `echo 3 > /proc/sys/vm/drop_caches` That should cause the system to drop the ZFS ARC along with the page cache. Once the ARC is below its new limit, it should honor that limit. – Andrew Henle Dec 02 '21 at 22:44
  • And a large ARC doesn't have to be a problem - it's only a problem if your system has sudden demands for large chunks of memory, especially huge pages. Because ZFS ARC release can be accurately timed with a sundial. So when you get a sudden demand for a lot of memory, if that demand can't be met without releasing a big chunk of the ZFS ARC, your entire system can stall while the VM system thrashes about waiting for ZFS. – Andrew Henle Dec 02 '21 at 22:48

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You can persistently reduce the ARC size by doing the following.

Edit or add a file named

/etc/modprobe.d/zfs.conf

Add a line as follows. This example line is for 1 gig of memory. So multiply the number by the number of gigs you want it to be sized.

options zfs zfs_arc_max=1073741824

After saving the file run the command

update-initramfs -u -k all

Then reboot to apply the changes.

Chris C
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