R660xs poor performance with 2025 datacenter

Question

I've got a hyper-V host we just purchased, and I installed 2025 datacenter on it. Dual Xeon gold 6534, 192 GB RAM, Perc H755, and 8 Dell 12Gbps SAS drives in two RAID10 arrays.

This is identical to a few dozen I have running 2022 with absolutely NO issues at all.

Used the lifecycle controller to create the array exactly as I have on every other Dell server I have deployed. Then used it to install the OS. Everything went fine, but it was odd that the OS install seemed to take quite a bit longer than it took to install 2022 on comparable systems.

Once it was installed, I grabbed the DVD tools and updated all firmware and drivers. Everything is current for both firmware and for drivers. Yesterday I even tried downloading the 03gc8 version 2.1.1.0 A00 version of the systems management application and ran it, and it found another BIOS update that didn't show yet on the support website's normal search portal.

Everything is just slow. Simple things like logging in take about 2 or 3 times as long. As does simple things like bringing up task manager, opening server manager, opening explorer, pretty much every single thing.

I created a few Hyper-V guests on it, also 2025, and it's the same performance problem. It seems like a disk bottleneck almost, but the host shows 0% CPU with all three Hyper-V guests running idle, 0% disk at idle, 0% network at idle. And doing things like opening Hyper-V manager doesn't show any impact, other than the CPU eventually hits 1%.

I thought I'd see if I could use previous drivers, since all the systems like this I have on 2022 have no issues whatsoever, but it won't even install on the OS, so there's been some clear changes between the OS architecture.

Has anyone else experienced anything like this? I've gone through the BIOS, RAID settings, caching settings, and everything is exactly the same as all my other Poweredge servers that have no issues, so I can only assume there is something different with 2025 that's just not working right for me. I've seen in other forums some people with similar issues but no resolutions, but there's also been people who are running 2025 on their Poweredge servers without any performance issues...

Thanks for suggestions.

Optimaus50 · Accepted Answer

I found a fix for the slowness/lagginess with Server 2025. I have several 660xs servers with NVMe storage having this issue, driving me nuts. Go into the BIOS and change the System Profile from the default "Performance Per Watt DAPC" to "Performance Per Watt (OS)". Per the link below "Performance Per Watt (OS): In this mode, no bus speeds are derated as they are in the Performance Per Watt DAPC mode, leaving the operating system in control of those changes". The default DPAC mode on these servers is too aggressive with power savings which kills performance.

https://infohub.delltechnologies.com/en-us/p/bios-settings-for-optimized-performance-on-next-generation-dell-poweredge-servers/

DELL-Young E · Answer

Hello, some OS vendors do have a guidelines on how to set it up. For example ESXi, https://www.vmware.com/docs/vsphere-esxi-vcenter-server-80-performance-best-practices

DELL-Chris H · Answer

JD Third,   We don't support performance issues, but what I would start with is ensuring the server is up to date on BIOS, iDrac, CPLD, Perc controller, drives, etc. The reason being is since the OS release is so recent I would make sure you have the server on the most recent updates.     Let me know if this helps.

JD Third · Answer

Well then nevermind, sorry for wasting the bits. And I went into detail how all drivers and firmware was current already. I'll just delete the post later. Again, apologies for asking a bad question.

DELL-Chris H · Answer

I would leave it for the community to respond on, it is just that we can't support it based on performance alone.

Jon Warburton · Answer

Did you find a resolution?  We are just about to open a case with Dell as we have a couple of 660xs that are running as backup servers and have been fine on 2022 but since installing clean builds of 2025 and updating drivers / firmware they have been running soooo slow, especially as soon as any significant disk IO kicks in.

JohnDean · Answer

Unfortunately no.  I've since replaced this deployment with an HP server since the Dell just was so bad with 2025 server, and even up to a couple days ago there were no updates for anything that may have made a difference.  Been holding my breath for a PERC drive update or firmware for my SAS drives or something...  So for now it's just sitting idle with no live VM's running on it until we see if they ever resolve it.  And I'm not about to deploy a new Hyper-V host running an OS that's 3 years old now...

Jon Warburton · Answer

wow, thanks for the quick response.   I'll try my luck with Dell tomorrow and if no luck then we may have to go back to 2022 as they were solid on that OS.

Jon Warburton · Answer

Out of interest were you running REFS on your data volumes?

JohnDean · Answer

I know, I've got like half a dozen of their servers running the older things.  Never a performance problem until this one with 2025 server.  Even blowing away 2025 and installing 2022 and replicating everything that did NOT work well with 2025 worked fine.  yet another clean install of 2025 and the issues are right there again.  So it is clearly simply an issue with drivers, NOT hardware, but Dell just isn't doing a THING about it...  Moving forward we may start going to HP servers instead since it has been nearly half a year and nothing has changed...

JohnDean · Answer

@Jon Warburton​ Nope, standard NTFS everywhere.  Absolutely nothing different than the 2022 server.

CyberTechs79 · Answer

I'm having this same issue, but with Server 2022.  Just seems laggy overall.  Is there a flaw in these servers with Hyper-V or overall flaw all together?

JD Third · Answer

@CyberTechs79​ When I was troubleshooting that first server in November and December, I blew it away and installed with 2022 and built some HV guests, and had no issues with performance.  When I blew that away and redid it again with 2025, still performance issues noticeable compared to 2022.  Still not resolved to my satisfaction, but there also has still not been a driver update for my PERC RAID controller yet either.  Seems just about every OTHER raid card has had a firmware or driver update, but not the PERC H755.

DELL-Young E · Answer

Hello, if I'm hearing this right@JohnDean- 2025 bad and 2022 good@CyberTechs79-2022 bad  so, these are two different issues, I'm thinking. If you would like us to have a look, you are more than welcome to start a new thread. You can send us your service tag by DM so that we can check warrant as well. https://www.dell.com/community/en/direct-messaging   All I can say for now deploy OS using LCC and use DSU to make sure driver/firmware updated.  related articles: https://www.dell.com/support/kbdoc/en-us/000130160/how-to-install-the-operating-system-on-a-dell-poweredge-server-os-deployment?msockid=1a5e8444c37364fc023690acc29e65bdhttps://www.dell.com/support/kbdoc/en-us/000130590/dell-emc-system-update-dsu?msockid=1a5e8444c37364fc023690acc29e65bd   Respectfully,

Jon Warburton · Answer

For us, after multiple rebuilds on 2025, firmware and driver updates, engaging with Dell support we were unable to get our two servers stable on 2025 under large IO stress. We have since rebuilt to 2022 and they have been instantly stable once again.

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R660xs poor performance with 2025 datacenter

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