Windows Server 2012 R2 Disk usage issue

Question

Our file server found such a problem.

1. The D drive shows that the available space is 3.75TB

2. The Lun of the memory used by the D drive shows that the available space is only 1.1TB

3. The last day disk optimization showed 81% space efficiency.

We want to know how much data can be added to the current D drive. Why is the space displayed on Windows D drive and Storage Lun different? 

The model of the storage is Dell SCv3020, we consulted Dell, but the other party told that it may be a problem with Windows space reclamation. 

Answer 1

Can you do repartition on the drive?

Answer 2

How do I fix low disk usage?

Answer 3

is the windows deduplication is enabled ??

Answer 4

a. 1.11 TB can be added to the current D drive.

b. The hard disk is total 15.36 TB while you has allocated only 14.25 TB to logical disk drive D. 

Answer 5

Typically, when you allocate a LUN in storage, related space is marked as used in the storage (except in the case that you select thin provisioning) even if you do not add any data to the disk in OS. So, I think at the OS level, you can use the 3.7TB space, + you can extend the disk by 1.1TB of available space in the storage. (Not recommended, usually allocated space on the storage side should not exceed 80%)

Answer 6

Why Does Your Server Disk Get Full?
Delete Outdated Backups. If you've never deleted server backups before, you might be able to free up gigabytes of space by deleting older backups.
Optimize SQL Databases.
Clean Up IIS Log Files.
Uninstall Third-Party Software.
Add More Server Disk Space.

Regards,
Peter