I just noticed something peculiar. We're using AlwaysOn availability in one of our environments with a read-only secondary replica. However, checking the .mdf / .ldf files for the secondary replica, it shows a modification time of several months ago. Similarly, using sp_helpdb 'DBNAME' in the secondary replica, it claims the space is significantly less than in the primary node.
Still, the DB shows as being Synchronized in SSMS object explorer, and upon reading the data in the DB, it's clear that the latest data is being replicated properly.
This is not a problem, I would simply like to understand what's going on, as I can't seem to find this information by googling for it. Why doesn't the space usage seem to be updated properly? Is it a question of permissions, or a symptom of the read-only mode itself, or what?