Xen accelerates ARM server race with version 4.5

1TB memory for guests on ARM and lots of VM-wrangling fun for admins

Version 4.5 of the Xen hypervisor is upon us.

Those responsible for the new release are chuffed to report they've packed a couple of dozen big new features in this time around, doubling the 4.4 release's count. And there's more to come: some useful stuff couldn't be squeezed into this release.

But before we get to those features, let's cast our eyes to the major contributors list. As one would expect, the likes of Intel, AWS, AMD, Citrix, Oracle and Verizon Cloud have been big contributors (so's the NSA, but don't say it too loud).

And this time around Cavium also makes the list. That's Cavium as in the mob that last year revealed a 48-core ARM SoC. That Xen can now allocate a terabyte of RAM to guest VMs should therefore not surprise, nor will the Xen folks' belief that this is a big advance that brings ARM servers into play like never before. The new release can also boot using UEFI and supports AMD's Seattle 64-bit server SoC.

That all adds up to a pitch from Xen that it can let users run up big VMs on the two major CPU platforms. Try doing that with your fancy Hyper-V or VMware.

Beyond that, the headline features are:

  • Xen PVH virtualization mode adding support for running in dom0 for Linux in Intel, a security-enhancer;
  • Introspection of HVM Guests, a hardware-isolation effort said to make it harder for kernel exploits, rootkits and other low-level nasties to get a foothold;
  • VM teleportation thanks to Coarse-grained Lock-stepping (COLO), which makes it easier to replicated to a second site. COLO's not fully done: Fujitsu tossed in a ton of code and this is expected to mature in Xen 4.6;
  • Improved realtime scheduling, a feature said to be mighty handy in embedded and/or automative applications in which VMs need to know exactly what resources they can get, and when they can get them. Data centre and cloud operator types will also like this as it will let them define resource levels for VMs;
  • More support for Intel's Resource Director Technology (RDT) to give a more granular view of how threads are using a CPU. Should help to silence noisy neighbours;
  • Systemd support, which will thrill the Devuan splitters.

Overall this looks a solid release that will please Xen users running just about any application, which may or not be a good thing seeing as the hypervisor is being advanced as suitable for running anything from a colossal cloud to a very small device. It also gives ARM server aspirants a … erm … shot in the arm.

New Xen versions land about every eight or nine months, so 4.6 should be with us by about October. By which time we should know rather more about the next version of Windows Server and vSphere 6 will probably be not far off its first service pack. ®

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