Resilient File System, aimed at large scale and data integrity: checksums, block cloning, mirror-accelerated parity and online repair with Storage Spaces. Windows cannot boot from it, and disk quotas and ODX, both found in NTFS, are missing.
Also called Resilient File System.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains ReFS in context, with comparison tables and the common traps.
Terms in this definition
- Integrity
One leg of the CIA triad: information remains correct and is only changed through approved means. Hashes, digital signatures and audit trails help guard it.
- Block cloning
VHDX merges and file copies on ReFS run fast because clusters are remapped rather than data being read then rewritten.
- Mirror-accelerated parity
A Storage Spaces Direct ReFS volume split between a mirrored portion and a parity portion. New data is written to the mirror first and later shifted to parity, which uses capacity more efficiently.
- Online management group
Workloads that may talk directly to or from the internet, or that need no virtual network at all, go in this management group. It is a sibling of Corp and Local beneath Landing zones.
- General-purpose v1
The older storage account kind (
Storage), which lacks access tiers, Archive and premium file shares and retires on 13 October 2026. Converting to ZRS requires first upgrading to GPv2, a one-way change. - ODX
Offloaded Data Transfer. A capable SAN moves or copies data internally, exchanging tokens rather than streaming it through the server; NTFS supports it but ReFS doesn't.
- NTFS
NT File System, the Windows file system; Azure Files honours its ACLs.
Related terms
- FAT32
Lacks file-level permissions, so Windows Server features such as FSRM won't work on it; use NTFS or ReFS.
- Integrity streams
Optional in ReFS: checksums on file data reveal corruption, which mirrored Storage Spaces can then repair.
- Limited Refs
An Azure Repos setting that cuts down how many refs the Git client and server exchange; it is advised for repositories holding over 10,000 refs.
- Scrubber
A ReFS background job that regularly verifies data integrity and, when Storage Spaces holds a mirror or parity copy, fixes damaged data using a good copy.
- Sparse VDL
A ReFS capability that zero-fills files almost immediately, so fixed-size VHDX files are created far more quickly.
- TLP
Labels threat intelligence with how sensitive it is and how far it may be passed on. In the upload API it goes in object_marking_refs; in the portal you just pick it.