topic Windows 2019 ReFS LUN shows more space consumed than reported by ONTAP in ONTAP Discussions

Windows 2019 ReFS LUN shows more space consumed than reported by ONTAP

pedro_rocha — Wed, 04 Jun 2025 10:33:30 GMT

Hello,

We have a space reserved LUN presented to a Windows 2019. Customer decided to use ReFS to format it. Today we noticed that from the windows host perspective there is more consumed space than reported by ONTAP CLI ou System Manager.

LUN is almost full (96%) from windows disk management GUI. ONTAP reports it as having (85%) of consumed space.

ONTAP is 9.5. The LUN is used for SQL Server data files.

Does anyone know what could be?

Regards,

Pedro

Re: Windows 2019 ReFS LUN shows more space consumed than reported by ONTAP

Mjizzini — Thu, 25 Feb 2021 02:31:11 GMT

Windows host does not auto-reclaim unused space for thin provisioned luns

How to reclaim space for thin provisioned LUNs using PowerShell for Windows

Re: Windows 2019 ReFS LUN shows more space consumed than reported by ONTAP

pedro_rocha — Thu, 25 Feb 2021 12:46:24 GMT

Hello

It is not thin provision.

It does not seem to bem a space reclamation issue. Storage side usage is
smaller than LUN/OS side.