Will expanding a volume delete my data?
Answer
Resizing volumes won’t affect existing data in the data volume,the data will stay intact after the process.
Here is the procedure to resize the volume.
1.Log in to your NAS from the web interface
2.Find Control Panel > System > Storage & Snapshots > Storage > Storage / Snapshots
3.Select a volume and click Manage and then Resize Volume in the new window.

Note: If the buttom of Resize Volume is grey out, please do a File System Check first
Note: Shrink a volume will stop all the services, you can't access the data at that time.
Reference link:
The data is not accessible duirng the following processes
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