Regarding the unit not knowing that storage will be attached, this was a add-unit operation and the service (postgresql) was already related to the storage subordinate. It might be an optimization, but it kind of knows already that it will get storage.
Regarding (b), interesting trick, I didn't know about it:
rwxrwxrwx 1 root root 29 Aug 19 22:06 main -> /srv/data/postgresql/9.3/main
drwx------ 15 postgres postgres 4096 Aug 19 22:04 main-1471644281
Regarding the unit not knowing that storage will be attached, this was a add-unit operation and the service (postgresql) was already related to the storage subordinate. It might be an optimization, but it kind of knows already that it will get storage.
Regarding (b), interesting trick, I didn't know about it: postgresql/ 9.3/main
rwxrwxrwx 1 root root 29 Aug 19 22:06 main -> /srv/data/
drwx------ 15 postgres postgres 4096 Aug 19 22:04 main-1471644281
So that seems to be ok.