Hot swapping is nothing new in the IT world. We’ve been able to replace hard drives and power supplies for years. And yet hot swapping within a single host has only really been possible in the realm of hardware.
Reboot-less OS upgrades are a thing of legend. It’s the software equivalent of a heart transplant and few technologies exist that can claim to pull this off. For example, Ksplice has been around since 2008 and was purchased by Oracle in 2011. Ksplice is capable of upgrading the Linux kernel by effectively stunning the system for about .07 milliseconds. During this time it updates any new kernel functions and maps instructions running in memory that use the obsolete functions to use the updated functions. Ksplice is a cool technology indeed, but what about complete OS upgrades?
The Register recently published an article about a new patent application submitted by VMware. Under this patent VMware proposes the ability to spin up a second operating system and move any running applications to the new OS. VMware being the virtualization giant that it is, you might think they’re talking about swapping OS’es at the virtual guest level, but this new patent filed 7/21/2016 specifically mentions hardware.
VMware has flirted with the idea of OS swapping for several years. In a patent filed back in 2013, VMware proposed a nearly identical technique for online hypervisor upgrades. Then, in 2015 VMware filed another patent for VM upgrades using virtual disk swapping. This technique proposes using linked clones where the secondary VM gets patched and applications eventually attach themselves to the secondary image.
The latest patent describes VMware’s proposed OS hot-swapping as follows. The original OS identifies a subset of hardware to be used for the second OS and partitions itself by quiescing the devices to be used by the second OS. This frees up hardware so that the second (updated) OS can be started and applications can be moved to the second OS. Once the applications are moved, the original OS is terminated and the secondary OS claims the hardware resources previously used by the original OS.
This is absolutely brilliant and one of the reasons I love VMware so much. They’re not afraid to attempt something like this to solve one of IT’s biggest problems. Not only is this great for OS updates, but could potentially be a solution for other scenarios such as all paths down (APD) when hosts can become unmanageable. The patent is still in the application phase and hasn’t been granted yet, but if it is this will give VMware a stranglehold on yet another game changing technology.