Windows 11 24H2 and 25H2 Small file copy performance issues with Isilon H400
and H500 clusters
As the title suggests, we have an issue with Windows 11 24H2 and 25H2 Small file copy performance issues with Isilon H400 and H500 clusters. Even on the LAN, we are seeing 35 files @ 20MB take 20 seconds or longer to transfer, and 5+ minutes when on the WAN in other locations, irrespective of latency or location. Has anyone else seen this? How did you resolve your issue, if so? Or, any tips to narrow down the root cause? We've spent a lot of time changing settings, checking Wireshark logs etc... and have come up empty handed thus far. Earlier versions of Windows and Server seem to work fine. Also, copies from our Win11 devices work just fine with other Windows-based machines when performing copies.
@Phil.Lam Been there, done that, and they are looking at logs, but they keep sending an article that claims SMB overhead for small files is "normal." Right, it is, but that's not the case with our performance issues. We're seeing excessively long copy and save times, and it's worse for WAN users.
Figure 6. Comparison of L3 cache and other SSD usage strategies.
You may need to select different SSD strategy based on the workload. For most of workflows with write component, it is recommended to select Metadata Read/Write SmartPools SSD option. For repeated random read workloads, the recommendation is to use L3 cache and you will observe latency reduced. Figure 7 shows the decision tree of various (non-L3 cache) SmartPools SSD options, and their requirements and dependencies.
@Phil.Lam Not sure that this is the correct path though, given we weren't having any issues, and then within the last 2-3 months the issue started presenting itself as we deployed 24h2.
SMB signingandSMB encryptionare known to slow down SMB transfers. The amount of the performance loss depends greatly on the capabilities of the hardware involved. The primary factors are the count and speed of the CPU cores, and how much CPU time is dedicated to other workloads.
Starting with Windows 11, version 24H2 and Windows Server 2025,SMB signing is requiredby default. We don't recommend turning off the SMB client and server signing requirement, as they provide significant protection against spoofing, tampering, and relay attacks.
@Phil.Lam I understand that SMB signing should be on, but the performance is so terrible that the clusters are unusable for small file activity whether it be saving, opening or copying them. However, on Windows Server operating systems, the performance is more than acceptable.
Phil.Lam
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Posted October 15th, 2025 20:19
@JMACND ,
please create SR so Dell support can investigate.