Windows ReFS Limitation


This document describes Clumio behavior for backup, restore, and file-level restore of virtual machines with ReFS drives. 

Clumio performs backups at the virtual disk level and indexes the data at a individual drive, folder, or file-level in the guest file system. For Windows, ReFS is one of many guest file systems used. Clumio does not currently support Backup Indexing for ReFS-based drives.


This is the expected behavior when a VM with independent disk(s) is protected by Clumio.

VM Backup:

  • Clumio VM Backups are taken at the VMware virtual disk level and do not exclude the ReFS drives, which are part of the Guest File System during backups.

VM Restore:

  • Full VM restore is not affected by the indexing limitation. If ReFS drives are part of the VM backup, you can expect all the drives, including ReFS, to be available as part of the restored VM.

Browse & Restore ( File / Folder level restore )

  • VM Backup Indexing is not supported for ReFS-based drives. You will see the following behavior in the Browse & Restore dialogue box, where the ReFS attributes are shown as "0 B(bytes)" and files inside the drives are not accessible for file-level restore. The workaround is to perform VM Restore.



Please contact [email protected] for questions or more information.