Recommended scheme for partitioning root file system into subvolumes following the Filesystem Hierarchy Standard

The Filesystem Hierarchy Standard (FHS) is the formal codification for root file tree on Linux installations, as inherited from earlier iterations of Unix and POSIX, and subsequently adapted. It standardizes the exact uses of the familiar /home, /etc, /usr, /var, and so on, from various historic differences of convention, and resolves where application-specific and site-specific file names may be added, or not. Basic Linux installations historically have placed the entire tree on a single file system, though some variations have utilized a separate partition for /home, presumably to facilitate backup and migration. More recently, Btrfs has gained increasing adoption, which allows a single partition to host various subvolumes. Subvolumes are appealing because they may be captured in snapshots, and require no pre-allocation of space. The mapping of subvolumes to nodes on the FSH appears to vary widely. Sensible standards and policies respecting such matters are important, for supporting optimal management of files on the system with respect to snaphots and related concerns. Following are some observations: - Debian appears to place the entire tree on a single subvolume beneath root. - Ubuntu appears to allocate a subvolume for /home, and another for the remainder of the root tree. - Arch Linux appears to extend the separation adopted by Debian by placing /var/log and /var/cache each in a separate subvolume. - openSUSE has a single subvolume for /var, and one each for /home, /root, /usr/local, /opt, and /srv, as well as one for the remainder of the root tree, a further one for each installed grub architecture. Have any standards emerged that have attempted to resolve the various design considerations, and to unify the approaches adopted by various operating systems? Has any agreement emerged concerning how to reconcile the functions of the various file tree nodes with policies concerning snapshots?