ReFS. Known issues

1. Repository server becomes unresponsive or crashes.
2. I/O performance on the server is reduced significantly.
3. The server experiences high memory usage.

Operating System
Use the following OS versions, which include fixes to the ReFS metadata management logic:

• Windows Server 2019 (requires Veeam Backup and Replication 9.5 Update 4 or later)
• Windows Server 2016 patched to at least September 2018 updates (KB4343884 or later)
• Windows 10 Pro for Workstations

Note: refs.sys driver version should be at least 10.0.14393.2457 or later. However, for best performance and security, we always recommend keeping all systems fully patched with the most recent Windows Updates .

Hardware
Backup repository must meet minimum system requirements. In particular, pay attention to the following in case of all-in-one backup appliances:

• CPU: ensure at least 1 core per each concurrent backup proxy task AND at least 1 core for each two concurrent repository tasks are available.
• RAM: ensure the repository server has enough RAM (at least the sum of RAM requirements for each individual Veeam component installed on the server).
• Storage: use 64KB cluster size when formatting the ReFS volume.

3rd Party Software
Uninstall the following 3rd party software that have been reported to cause ReFS stability and/or performance issues:

• Antivirus software (except Windows Defender)
• Microsoft Configuration Manager Client