Desktop virtualization brings similar challenges to the environment. Like server virtualization it provides consolidation, but on a larger scale. Thousands of desktops are now served by a few physical hosts. While the ongoing I/O demand is not overwhelming for most storage systems, there is the morning login event (or boot storm) that exposes a bottleneck in most storage systems. Less concerning is the’ logout event’ which is still problematic, and while it doesn’t affect users as they leave for the day, it does impact the performance of overnight processing jobs.

In both cases, the shared storage device enables capabilities like live virtual machine migration and increased availability of virtual servers and desktops, but also has the potential to create a bottleneck. The storage bottleneck limits the amount of virtual machines that can be deployed per host. It also hinders the migration of more mission critical or tier 1 applications for fear of creating even greater performance challenges and more importantly, reduces tier 1 application response times. This results in the storage I/O performance becoming a key roadblock to realizing an increased ROI from the server virtualization investment. This bottleneck typically occurs at one of three points in the storage I/O chain: the storage network, the storage controller or the storage devices.

Addressing The Storage Bottleneck Pain Points

Storage infrastructure bandwidth problems are relatively easy to resolve. While virtual machine density increases the amount of traffic per I/O port the speed of those ports can be upgraded substantially. 4Gb Fibre can be upgraded to 8Gb and multiple 1GbE connections can be upgraded to a single 10GbE interface or made to leverage FCoE for storage connectivity. Even further, 16Gb FC is set to begin shipping in late 2011. Additionally, these cards now have the ability to provide VM prioritization on storage traffic so that mission critical applications can be assured a minimum level of bandwidth.

More challenging is the storage controller itself which, especially if it has a dual controller architecture, can quickly become the bottleneck as the virtual environment grows. This is compounded when I/O capabilities are added to the other side of the storage channel, the disk drives. As storage companies add solid state storage devices to their systems customers are quickly finding out that the storage controllers cannot provide the solid state drives with the performance required to extract their full performance.

An alternative strategy is to use a solid state storage system, like those available from Texas Memory Systems. These storage systems essentially offload the performance demands from the primary storage system and provide a perfect compliment to those systems. They are designed from the ground up to handle the high traffic I/O that busy virtual machines or virtual hosts will demand and are able to deliver maximum performance from their internal flash memory. In the last article we discussed how to integrate these systems to coexist with legacy storage, and in the first we discussed how the capabilities of server virtualization makes them cost effective.

The Power Of Solid State Performance

Leveraging solid state storage in a virtual server environment, assuming the storage connectivity is capable, can have a dramatic impact on the effectiveness of the project. Much of the administration time for a virtual environment is spent on fine tuning the storage performance of that environment. This often means creating and managing very large RAID groups and dealing with capacity inefficiency caused by those RAID groups. It also means trying to constantly balance I/O loads between the hosts, VMs and storage. The abstraction of server virtualization makes performance tuning difficult since the culprits are difficult to identify.

Moving high performance workloads to a dedicated solid state storage system resolves most, if not all, of the performance problems caused by demanding VMs, better balancing the I/O workload between two systems. The solid state system, since it can respond to almost any level of I/O, can provide better performance to the virtualized application than was possible when attached to mechanical storage. This process also allows for normalization of RAID protection configurations on the legacy systems. The result should be a significant reduction in time spent tuning storage and increased capacity utilization.

A key benefit of this combination is that tier 1 applications can be virtualized without a risk of performance loss and overall machine density can increase significantly. This allows the ROI of the virtualized environment to be realized even sooner as well as allowing more applications to benefit from the value of virtualization.

Solid State Storage And Virtualization - The Perfect Compliment

Augmenting legacy storage with a dedicated solid state storage device may be the perfect remedy to the I/O performance problems that server virtualization often creates. By offloading the demanding hosts or VMs to the solid state device the longevity of the legacy system can be increased and the virtualization project enabled to grow and become more profitable. Finally, it returns the most precious resource, staff time, back to the data center, since time spent continuously tuning the environment is almost entirely eliminated.

Texas Memory Systems is a client of Storage Switzerland

George Crump, Senior Analyst

Enhancing Server and Desktop Virtualization with SSD Series

Part I - Cost Justifying SSD
Part II - Integrating SSD into a Virtual Server or DT Infrastructure

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Part III of Enhancing Server And Desktop Virtualization With SSD