you may study CMS-solutions like
- wordpress production and update from staging site
- update from git where the production is a local repository and is going to recieve the modification from main repository (Drupal)
- and more
for small updates can be done fast and maybe withoun to enter the site to maintenance mode
there are other cases, when the disks are in mirror format, then you split the mirror into a-mirror and b-mirror, users work with a-mirror, you update the b-mirror and then recreate the mirror in order to perform the update
I hope to help.
