The following information is based on the following articles:
- https://blog.thestateofme.com/2020/11/16/expanding-synology-volume-beyond-16tb/ -- which applies to DSM 6
- https://github.com/jmiller0/how-to-fsck-on-synology-dsm7
Old Synology NAS generations had a limitation of 16TB per volume.
A nice feature of Synology is that you can buy a new NAS and move the drivers from the old NAS to the new NAS and simply continue. However, when you do this, the volume is still limited to 16TB as the filesystem is 32bit. DSM does not offer an option to convert the filesystem to 64bit via the UI.