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XenSummit has been a tremendous success this year. Thank you to all the speakers for contributing and to all the attendees for making XenSummit an interactive and fun conference with lots of discussions. You can find presentations on slideshare and videos on vimeo. We will also embedded both in the agenda. The slides are also available for download as zip file.

Building a Distributed Block Storage System on Xen

Xen has long been a core building block for data center virtualization solutions, and is widely regarded as the predominant cloud hosting platform today. Selecting an open hypervisor platform is often the simplest choice in deploying a new cloud platform, with the hardest decision quickly becoming the choice of storage backend. Choices range from various open source options such as LVM over block-based iSCSI or ATAoE through to high-end NAS or SAN disk array solutions. Having the most optimal, open cloud environment, however, rests heavily on a comparatively open storage system. Unfortunately, most open source approaches to cloud storage today still depend on centralized or replicated metadata among a small number of nodes. Not only does this often lead to a single point of failure, but it also significantly limits the openness and scalability of the cloud environment since bottlenecks can quickly develop along the centralized I/O point as the number of hypervisor nodes scales out.

In this session, Julian Chesterfield, former XenServer storage architect and current OnApp Storage and Virtualization Architect, will advocate the deployment of a new cloud scale approach to storage. Through decentralized storage management, and exposure of direct attached storage located within hypervisors, a dynamic and scalable distributed block store can be composed. As the number of hosting end points scales up to accommodate the virtualization workload demand, so too can the storage capacity and I/O processing capacity. Using a distributed block storage approach in the cloud, companies and service providers can decentralize their I/O paths to avoid any points of contention or I/O bottlenecks. By distributing them over the entire platform, each I/O path is independently optimized to deliver far greater performance and scalability - the same scalability one would expect to accompany an open, Xen-based hypervisor platform. What's more, the latest cloud storage innovations allow this distributed approach to be implemented using commodity Ethernet and storage hardware, thereby creating an inherently scalable and cost-effective approach to storage in the cloud, with a far more consistent level of performance over vast ranges in the number of end-points.

Such a decentralized, distributed storage approach is especially valuable for service providers who typically start out with a small number of servers and then often find themselves quickly scaling up as their user base grows. With traditional storage solutions, requirements for such rapid scalability cannot be met or easily provisioned for as it's very difficult to predict growth or demand. A distributed block storage model, however, can easily accommodate the scalability such providers need as they grow their business.

This session will also discuss how a decentralized cloud storage system that exposes direct attached storage in hypervisors is better able to take advantage of two key Xen features: namely, the ability to use dedicated storage controller hardware passthrough to a driver domain to isolate storage access within a hypervisor and the ability to use both dedicated storage and network resources to create a logically isolated high-performance appliance using shared server resources while still generating the equivalent performance of a stand-alone, dedicated storage appliance, as you would get from a traditional SAN array.

Julian Chesterfield, OnApp

Julian Chesterfield heads the development team at OnApp's R&D division in Cambridge, UK, and leads development of OnApp's cloud storage platform. Julian has deep experience and expertise in storage virtualisation. He was an early member of XenSource, the Cambridge University spinout company that developed Xen, the open source hypervisor acquired by Citrix in 2008. Before joining OnApp he was the architect and development team lead for storage in the XenServer product division.

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