Storage caching: EMC FAST Cache and VFCache
Combining storage tiering with storage caching further enhances storage performance. EMC's FAST cache utilises EFDs to extend existing cache capacities by up to two terabytes (TB) and optimises storage performance by providing immediate access to active data. By doing this, it absorbs spikes in application workloads, increasing the performance of read and write operations. Data now gets served out faster, reducing storage latency while enhancing the end-user experience.
Storage caching with FAST can also be complemented with server-side caching delivered by EMC VFCache. VFCache delivers storage caching in the form of a PCIe card installed on the host server, but managed by the EMC storage infrastructure. By caching virtual desktop activity at the host server side, organisations can accelerate I/O and improve application response time by keeping only a copy of the "hottest" data on the PCIe card in the server.
This is particularly useful for web applications, OLTP and email applications which typically see high user-traffic and applications which require high IOPS. With reduced latencies, web pages for example, load faster, significantly improving the end-user experience of virtual desktops.
Software-based storage caching represents yet another approach to enhancing storage for VDI. It forms part of a greater software-defined storage strategy centred on the virtual machine (VM) and leverages on a storage hypervisor, to dynamically coordinate virtual storage resources to accommodate the erratic I/O patterns.
A software-based storage caching brings storage closer to the VM workloads and better positions it to handle the random IO patterns. With software-based storage caching, organisations bypass the need to fully provision storage for VMs or continually adding physical storage resources in an effort to accommodate the erratic and high volume of I/O. Such an approach effectively optimises existing storage capacity while minimising storage costs.
Realising the promise of VDI with the right storage infrastructure
Storage remains a fundamental part of the VDI equation. Organisations have to get storage right before they can successfully reap the benefits of VDI. With an intelligent end-to-end tiering environment-where data is automatically matched to storage tiers based on their activity level-combined with storage caching and/or software-based storage caching, organisations are better able to balance storage costs against application performance in their VDI deployments; ultimately making good the promise of VDI.
Tom Zack is President South East Asia, EMC.
 Eric Siebert, How to avoid VDI boot storms using SSD, SearchVirtualStorage., April 2011,
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