Microsoft enhances availability of Azure virtual machines by introducing Memory-preserving updates

Microsoft Azure is by design a platform supporting cloud native applications. Cloud native means the application has redundancy built-in because it assumes the cloud platform does not offer a high availability to applications.

However Azure is extending to support legacy, enterprise applications by introducing a technology called Memory-Preserving Updates. 

Platforms like Amazon AWS and Azure do not have availability options like vMotion/Live Migration. Hardware components like power supplies are not redundant. Racks have a single top of rack router. On the other side of the IaaS cloud spectrum are VMware clouds like VMware vCloud Air. These platforms offer redundancy in the infrastructure.

Microsoft Azure will never have a Live Migration feature. The network bandwidth required to live migrate 1000s of virtual machines is enormous. Microsoft prefers to use bandwidth for East-West traffic between virtual machines/applications.

Google however extended the support from not just  cloud native apps to enterpise, legacy app. In December 2013 Google added a feature called Transparent Maintenance to Google Compute Engine. Transparent Maintenance uses a live migration technology to move virtual machines from one host to another without downtime.

Microsoft silently added in January 2016  a feature to the Azure platform which enhances the availability of single instance virtual machines (virtual machines not part of an availability set). Previously Azure hosts had to be rebooted after Microsoft applied patches to the host operating system (modified Windows Server Hyper-V core installation). This resulted in downtime for the virtual machines running on the host.

With the new Memory-preserving updates technology virtual machines are pauzed for a maximum of about 30 seconds while certain classes of software updates are applied to the host operating system. On average a virtual machine will be pauzed for about 9 seconds, short enough to not disconnect network connections or disrupt applications.

Unknown is what the effect of memory-preserving updates technique  will be for the Service Level Agreement. Currently Microsoft does not offer a SLA on single instance virtual machines. In 2015 Microsoft Ireland told partners that Microsoft will offer a SLA for single instance VM’s in the near future.

The Microsoft Build conference is used by Microsoft to announce new features. End of March 2016 we might hear more details.



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