Hi Chris,
This weekend past, I did create /opt and /var as subvolumes. For the empty /opt, it was
easy. For /var, it took the live ISO to help with moving directory /var to subvolume /var
I also intend to do the same with /sys on this, my beta system, Later this week I will
install the "release version" on a second drive as a second system, when it is
available.
The rational for my doing the subvolume exercise is the following:
1) Under default installation, each snapfile of root has a copy of all subdirectories
including active /var, and /sys. I noted that /var/log and /var/cache is rather volatile.
My SSD size is 120gigs
2) By isolating /var, /opt and /sys the root snapshot becomes less bloated.
3) The /sys directory rarely has changes according to my survey of directory and file
dates. One subvolume taken when there is a change is OK for me.
4) But /var/log is quite active, as is /var/cache. I will be using btrfs defragment on
/var.
5) Having /var as nodatacow puts /var to the same risk level as when /var was on the ext4
system.
I will be using fstrim -a (to do SSD trims) and I want to user snapper, to manage the
subvolume snapshots. The generations of snapshots for /var and / will be my objective.
I will be using crontab and a script to take snapshots just before the script launches
"sudo dnf update -y".
This switch to btrfs is a learning experience for me. Fedora is my passion, From my
studies, I may discover that you are absolutely right to state that I do not need to make
the extra subvolumes.
The advantage I have over you is my career. It is called "retirement".
Retirement comes with spare time to study, to learn, to write code, to explore, experiment
and to share experiences.