Direct Mode didn’t work on ReFS formated Cluster Shared Volumes

Hi,

why is direct access not possible with a ReFS format CSV volume?

Instead of direct access, all reFS formatted CSVs that are provided by a SAN runs with  "FileSystemRedirected".

This behavior is critical because the "FileSystem Redirected" mode, compared to direct access, has up to 90% or more performance losses depending on the environment.

Neither the fact that ReFS formatted CSV only run in "FileSystem Redirected" mode nor the associated performance penalties are mentioned in any official Microsoft statement.

On the contrary, Microsoft actively recommends using ReFS for VHDX files.

That is why, like many others, I have formatted the CSV with ReFS since the server in 2016, because I hoped that this would be an advantage for the customer systems.

Unfortunately, this procedure led to the opposite and it was not easy to find the reason for it. Mainly because Microsoft has absolutely nothing documented about this behavior.

I personally had to postpone more than 100 TB of data on various customer systems over the past few months in order to eliminate this problem and to bring the CSV formatted with ReFS back to NTFS. This action cost my company a considerable amount and also led to massive annoyance of the customer.  

However, if you know what to look for, you can now find a lot of posts on the Internet that confirm this behavior.

Here are a few examples.

https://github.com/MicrosoftDocs/windowsserverdocs/issues/2051

https://www.hyper-v-server.de/hypervisor/performance-probleme-hyper-v-cluster-mit-san-storage-und-csvs-mit-refs-formatiert/

https://techcommunity.microsoft.com/t5/failover-clustering/understanding-the-state-of-your-cluster-shared-volumes/ba-p/371889

https://www.windowspro.de/marcel-kueppers/refs-ntfs-vor-nachteile-dateisysteme-server-2016

https://www.wowrack.com/blog/microsofts-latest-system-refs-compared-to-ntfs/

https://4sysops.com/archives/windows-server-2019-cluster-shared-volumes-best-practices/

https://social.technet.microsoft.com/Forums/ie/en-US/6b2dcc4f-e735-4700-81f3-df45d94e7e01/refs-for-a-hyperv-csv-volume?forum=winserverhyperv

https://forums.veeam.com/veeam-backup-replication-f2/latest-veeam-community-forums-digest-oct-2-oct-8-t46019.html

Therefore, I now spare myself any further details and come directly to my demand.

If ReFS does not fundamentally support direct mode, then I also expect Microsoft to publicly clarify it accordingly and also clearly indicate which disadvantages could arise if the CSVs are formatted with ReFS.

If it should work and there is only a bug in between, please finally fix it. This problem has existed since Server 2016, so enough time should have passed to fix the problem.

Best Regards from Germany

Alex