I add a comment to this topic, since I just have an issue with ReFS and our Dell Compellent.
We use our Compellent as backup repository and therefore provided a 30TB LUN.
Our Veeam server is a Server 2016 and the volume is formatted with ReFS.
Over the last year I was totally satisfied with the performance. Backup speed was great and the weekly synthetic full backups also took only 10minutes.
Now this week I had this issue:
Noticed that the Compellent shows a warning of only 4% free disk space left of the 30TB.
While the Windows ReFS Volume still shows about 40% free space.
Talked with Compellent Support:
Problem is, that ReFS supports no TRIM/Unmap. Therefore deleted data will not be marked again as free space.
I did not know that, even if it was declared in the MS technet.
Dell Support clearly recommended to use NTFS in this case.
So I guess that I will reconfigure everything back to NTFS which might result in lower performance and space savings.
But would be glad if anyone has better recommendations or comments