Microsoft gives Hyper-V ceilings a Herculean hike

Windows Server 2025 will let you run a VM with 2,048 vCPUs, 240 TB RAM, and 68 network adapters

Microsoft has announced new scalability ceilings for its Hyper-V hypervisor.

"Please read carefully. These are not typos," wrote Jeff Woolsey, Microsoft's principal program manager for Azure Stack HCI, Windows Server and hybrid cloud.

That warning came in the first of a series of Xeets in which Woolsey revealed that VMs under Hyper-V in Windows Server 2025 can run 2,048 virtual CPUs and 240 TB of memory. A Microsoft article adds a little more detail: each VM can support up to 256 SCSI disks, four SCSI controllers, and virtual disks can reach 64 TB apiece. You can also have 68 virtual network adapters, alongside four virtual fiber channel adapters.

Tragically, you'll have to make do with a single virtual floppy drive.

Hosts for Hyper-V reach even greater heights – with 4 PB of memory permitted.

Clusters can scale to 64 nodes and host 8,000 VMs.

Most of the above numbers stay the same under Windows Server 2022, other than the vCPU count, which drops to a mere 1,024. The 240 TB memory ceiling is a big lift for Windows Server 2022.

Some of the large numbers above can only be reached with Gen-2 VMs, which were designed to scale higher and include Trusted Platform Modules and the Unified Extensible Firmware Interface. Gen-2 VMs will become the default under Windows Server 2025.

Microsoft's article in which the maximums are revealed instructs users to "plan for Hyper-V scalability in Windows Server" – an imperative that reflects the fact Windows Server 2025 is currently in preview.

But news that Microsoft-managed VMs can scale higher will be welcome for a couple of reasons.

One is that some workloads need monster VMs. SAP can require tens of terabytes of RAM. AI training workloads will need truckloads of storage and memory. It just makes sense for Microsoft to make sure its platform can handle those requirements.

The other reason is that Broadcom's acquisition of VMware has given virtualization shops a good reason to consider their options. While Hyper-V and its adjacent tools – like the System Center Virtual Machine Manager – are generally rated inferior to VMware's stack, Broadcom's new licensing plans have angered many users. And it's a rare IT operation that doesn't have some entitlement to Windows Server and therefore Hyper-V.

Woolsey also points out that Hyper-V is also present in Xbox – the gaming console uses it to isolate games and other workloads. The Register mentions this as idle speculation about the kind of entertainment experience that would become possible if Xboxes ever scaled anywhere near the hosts Hyper-V can now inhabit – with the added essential speculation about whether it could run Crysis. ®

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