scripts-admin-debian/miscellaneous/readme_zfs_8gb_arc_limit.md

To limit the amount of RAM allocated to the ZFS ARC cache to 8 GB on TrueNAS, you can adjust a system configuration setting. Here’s how to do it:

1. Access the TrueNAS Interface: Log in to the TrueNAS web interface.

2. Open the Shell: Go to the top menu and click on Shell to open a terminal.

3. Modify the ZFS Configuration:

   • Enter the following command to limit the ARC to 8 GB:

     sysctl vfs.zfs.arc.max=8589934592
     

   • This command sets the maximum ARC size to 8 GB (8 GB in bytes = 8589934592).

4. Make the Change Persistent:

   • To ensure this setting applies on reboot, add it to the startup configuration file.
   • Use the following command to append it to sysctl.conf:

     echo "vfs.zfs.arc.max=8589934592" >> /etc/sysctl.conf
     

5. Restart the System: It's recommended to restart TrueNAS to make sure the setting takes effect.

This will effectively limit the ZFS ARC to 8 GB, allowing more RAM to be available for other processes.