systemctl enable tmp.mount

Consider the practice of mounting the /tmp directory on a tmpfs memory based filesystem, as can be done with: systemctl enable tmp.mount And consider the following: > **one justification:** The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing. - > **another justification:** Some applications writing files in the /tmp directory can see huge improvements when memory is used instead of disk. Is disk caching always in effect? By that I mean when you write to **any** folder (not just /tmp) you are probably writing to RAM anyway until such time it gets flushed to disk... the kernel handles all this under the hood and it is my opinion I don't need to go meddling tweaking things. So does doing systemctl enable tmp.mount has any real value, if so what? Also (in CentOS-7.6) I am testing this to try and understand what's happening I am experiencing: - CentOS 7.6 installed on one 500GB SSD with simple disk partitioning as - 1GB /dev/sda1 as /boot - 100MB /dev/sda2 as /boot/efi - 475GB /dev/sda3 as / - PC has 8GB of DDR-4 RAM - if I do just systemctl enable tmp.mount I then get - 3.9GB tmpfs as /tmp How is this tmpfs /tmp at 3.9GB any better than the default way which would (a) first have up to ~8GB based on RAM thanks to disk caching and (b) then when disk caching at capacity based on 8GB of RAM there is > 400GB of disk available to use ?