Toronto based start-up Gridcentric, is developing a technology that it refers to as Virtual Memory Streaming that has the potential to reshape the economics of VDI, and deliver the holy Grail of a VDI desktop for less than the price of a PC.  It should come as no surprise to hear that the single biggest performance challenge that all large VDI environments face is the boot storm. The Windows boot and logon processes generate many times more IOPS traffic than steady-state user operations. So much so that in poorly specified systems a boot storm will overload the storage infrastructure, starving Windows of resources and leading to excessively long start-up times.

The challenge of overcoming storage bottlenecks has led to many innovative solutions being put forward to overcome these challenges. Storage vendors have worked hard to optimize their caching technologies to improve VDI performance, at the same time vendors of NAND-flash based caching controllers such as Fusion-IO are also contributing to overcoming the limitations of conventional storage, while vendors such as V3 Systems are offering high-performance servers with tightly coupled SSD storage to create a desktop cloud delivering sessions that are in many cases faster than conventional desktops. Hypervisor vendors have built caching technologies directly into the hypervisor to improve start-up performance, while start-ups such as Atlantis Computing and Virsto have introduced their own dedicated solutions that further improve on the native capabilities offered by the hypervisor vendors. Now, however, another start-up is entering the scene with an innovative new approach to tackling the book storm problem while at the same time significantly increasing the number of sessions a VDI host can support.

Toronto based start-up Gridcentric, is developing a technology that it refers to as Virtual Memory Streaming that has the potential to reshape the economics of VDI, and deliver the holy Grail of a VDI desktop for less than the price of a PC. Gridcentric Virtual Memory Streaming (VMS) combines multiple hypervisor memory management techniques including highly-granular transparent page sharing, cloning, and read caching, with an innovative snapshotting process, which work together to eliminate the boot storm IOPS and significantly reduce the memory footprint of individual virtual desktop sessions.

Rather than attempting to accelerate the server or storage infrastructure to mitigate the impact of a good storm, Gridcentric’s approach is to eliminate the storm altogether. VMS eliminates the boot storm altogether by provisioning desktops from a vDisk containing a “golden snapshot” of a pre-booted virtual desktop –If there are no desktops to boot, there is no boot storm to address. As the snapshot is streamed from disk it is copied in memory to create a working copy which is then personalized on-the-fly by VMS to ensure that all unique configuration requirements are honored, essentially performing a Sysprep as the desktop is readied for use. Once this step is complete, the virtual desktop is released to the VDI connection broker. VMS maintains a cached copy of the golden snapshot allowing subsequent virtual desktops to be provisioned almost instantaneously.

Gridcentric VMS does not attempt to address I/O loading caused by user logon, profile management and application startup. However as post-boot IOPS is both an order of magnitude smaller than boot IOPS and consists largely of read operations which are readily address through existing caching and streaming technologies, this is not that significant an issue.

Preliminary testing of pre-beta code suggests that VMS will be capable of dramatically reducing IOPS load during virtual desktop startup, achieving a 70% IOPS reduction over conventional SAN storage. At the same time, VMS enables a memory overcommit of more than 100%, significantly greater than that achieved by any memory overcommit technologies offered as part of currently available hypervisors. Together, the is improvements can significantly lower the cost of VDI, especially on memory constrained optimization platforms.

Initial development for Gridcentric VMS is being done for Citrix XenServer. The availability of VMS for other hypervisor platforms has not yet been announced. VMS only works with non-persistent (pooled-random) virtual desktops. Support for persistent desktops does not appear to be likely at present, however given the number of competing solutions that can provide personalization for non-persistent desktops this may not be a major handicap.

Gridcentric are currently recruiting beta customers.

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Simon Bramfitt (128 Posts)

Simon is an independent industry analyst covering enterprise desktop, mobile and application virtualization, delivery and management technologies.

He is an experienced solutions architect with unmatched insight into the challenges of designing large (200,000 seat plus) high availability presentation and desktop virtualization systems.

Simon was invited to join the Citrix Technology Professionals (CTP) group in May 2010 and joined the Virtualization Practice in September 2010

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