found it
During system boot, the file /etc/modprobe.d/zfs.conf is auto-generated to limit the ZFS ARC to 1/8 of installed memory. This can be overridden if necessary by creating a custom 'config/modprobe.d/zfs.conf' file. Future update will include ability to configure the ARC via webGUI, including auto-adjust according to memory pressure, e.g., VM start/stop
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