Reported trash size stuck at 7 TB alhough there is 0.8 TB trash occupied space on the disk

Node Operators troubleshooting
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This sounds like an NTFS. If so, you need to check and fix errors on this disk and perform a defragmentation as soon as possible.
The next steps are:

  1. NTFS Disable 8dot3name
  2. [Solved] Win10 20GB Ram Usage - #17 by arrogantrabbit
  3. Some reported that disabling an indexing service for the disk could improve a performance a little bit, too

If you would still have issues, then, well, you may improve it by adding an SSD as a storage tier using the PowerShell, or using a Primocache.

Do not forget to enable an automatic defragmentation for this disk, if you disabled it (it’s enabled by default).