Proxmox – ZFS allocated 50% of RAM

This is to restrict the memory that ZFS allocated.

As a general rule of thumb, allocate at least 2 GiB Base + 1 GiB/TiB-Storage. For example, if you have a pool with 8 TiB of available storage space then you should use 10 GiB of memory for the ARC.

echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max

To permanently change the ARC limits, add the following line to /etc/modprobe.d/zfs.conf:

options zfs zfs_arc_max=8589934592

This example setting limits the usage to 8 GiB (8 * 2³⁰).

Refer – https://pve.proxmox.com/wiki/ZFS_on_Linux#sysadmin_zfs_limit_memory_usage