Data Protection Manager storage usage
DPM stores everything on a local 20TB RAID (formatted in ReFS). The system was running DPM 2019 a week or so ago and total storage usage was about 11TB. It had been online for several years before I got to it so storage usage was stable. I upgraded to DPM 2022 since we had to move all the VMs from a 2019 Hyper-V cluster to a 2022 Hyper-V cluster, so we had to update DPM to be able to support the new cluster. I also made some adjustments to the protection jobs, pulling out any old VMs that weren't in use anymore and adding a few "new" servers that weren't currently in DPM. Within less than a week the storage usage has skyrocketed and the drive is now almost full. I deleted a bunch of old retention points yesterday to get some space back, but DPM went and gobbled most of it up last night. I am puzzled why the usage is so high for just 10 days' worth of recovery points. The environment that we're backing up isn't big. I have searched for old recovery points that might have been missed the first time around and came up with about 200GB, which is hardly anything. Deduplication isn't an option since the DPM server is physical. When I checked this morning there were 857GB free on the storage drive. Now (2:40pm) there are just 348Gb free, but the only DPM jobs that have run since this morning are synchronization jobs and Monitoring shows they transferred less than half a GB. So why is DPM showing half a TB gone from free space? I was wondering if there's some other issue that might be affecting storage usage, perhaps to do with ReFS. Any other ideas would be much appreciated!
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
