I have a Synology DS414 NAS device and I would like to allow my whole family to perform backups of their Macs on the NAS storage.
So far I have followed the official Synology guide and created a shared folder to back up my Mac on the NAS. Official manual states:
Synology NAS provides compatibility for backup with Apple Time Machine. Mac users can back up their data to the shared folder of the Synology NAS without problem. Go to Control Panel > File Services > Win/Mac/NFS, tick Enable Mac file service, and choose a shared folder from the Time Machine drop-down menu. The chosen shared folder will become Time Machine's backup destination.
Problem is that the drop-down menu allows you to choose only one shared folder. My question is: How can I create a separate folder for every single user, so that everybody could use Time Machine?
When backing up over the network, Time Machine creates a disk image file (technically a "sparsebundle", which is actually a folder full of files, but Finder presents it like a single disk image file). Each Mac will create its own disk image in the one shared folder. They won't conflict with each other.
If you have multiple users on a single shared Time Machine volume you will soon run into serious performance and file management issues due to the huge number of files. Even though every backup has its own sparsebundle image, they are in fact directories with lots of small 2MB files inside. So having each backup on a separate volume will be a lot more efficient and easier to manage. If you no longer need a backup you just erase a volume, as opposed to deleting the backup image which can take days to process.
Here's what I do. DSM can only propagate one Time Machine backup, but you can specify which volume to use in the DMS settings (Control Panel/Mac File Services). You only need to do this when you wish do perform a system restore (Bonjour) or when setting up Time Machine backups on a client system. BTW, you can also simply mount the system (SMB since 10.13) and specify to use it for Time Machine backup. It will remember the login.