My Synology NAS DS216j has two x 2TB drives in a RAID configuration.

Storage Manager shows 1.37TB capacity as in use, which surprised me when I noticed as I do not have anywhere near that volume of data stored.

Running a Storage Analyser report on the entire volume shows I am using roughly 300GB.

Why/how is the 1TB reported by Storage Manager not accounted for? I suspect this space may be taken up by deleted files, but where these are saved and how to delete them so far escapes me.

Any idea what is going on here?

  • 1
    When using SHR or SHR-2 HDD protection as your RAID type, the Unused space will be automatically reserved for future expansion. On the contrary, Unused space under other RAID types indicates the space that can't be utilized and is thus wasted. [Via: synology.com/en-global/support/RAID_calculator ]
    – Danfossi
    Oct 31, 2019 at 15:40

1 Answer 1


The issue was that with an application named Cloud Station Server which keeps a database of previous versions of files. It can be configured to not save old versions of files, however as I not use this application I opted to uninstall it instead. Job done.

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