Backing up macOS with Time Machine to a Synology NAS
Google returns several guides on how to backup your Mac using Time Machine with Synology. I’ve discovered that many of them, official and otherwise, cause problems for the common situation where you may want to access your NAS for purposes in addition backing up your mac (e.g. storing and sharing files).
Other guides, specifically, advice creating both a dedicated user and a dedicated shared folder for Time Machine. The official guide recommends, then, creating a user-level quota. Other guides recommend creating a folder quota.
If you already have a user account for yourself, however, you do not need to create a separate user account. You can instead either, or both:
- Set a quota for the backup folder
(Control Panel > Shared Folder > Select/Edit > Advanced > Enable Shared Folder Quota) - Set a user-specific quota for the backup folder
(Control Panel > User > Select/Edit > Quota)
These two options are illustrated below.


What’s wrong with a dedicated backup user?
Having a dedicated backup user sounds like a good idea for separating services by user, but in practice, I’ve (personally) found:
- No advantage for the extra steps
- MacOS times network operations out when I connect to the network location as two different users (a time machine user for backups, and myself for accessing files)
This will change
Technology changes fast. For context, I’m writing this article in August 2017 using DSM 6.1.3–15152 Update 2 and macOS Seirra 10.12.6 (fresh install). Perhaps the official guide will be updated. Perhaps Apple will fix the network problems making the user-quota solution a bit more acceptable.
A note about Time Machine
Finally, three notes about macOS and Time Machine in general:
- Time machine is designed to use an entire volume until it runs out of space. That’s why quotas are important here.
- Time machine has saved my data twice from macOS. The third time I used it, however, the backup image got corrupted and I’m thankful I kept a third backup. I don’t know how it was corrupted, but a different backup for a different computer on the same Time Capsule continues to work. All signs and tests point to a software, not a hardware, issue.
- Consider setting up time machine to exclude backing up certain items on your hard drive for recovery. Right now, I’m excluding, among other data, backing up (a) Applications and (b) my Google Drive folder. Although this is absolutely not best practice for all situations, if my mac dies again I’m happy to reinstall applications and I actually prefer re-syncing Google Drive. Plus, Google Drive currently advices a re-sync.
