IoTurbine software integrates at both the VMware hypervisor and guest operating system levels to provide a write-through read cache implementation to the storage system shared between virtual machines and multiple physical servers. The approach's main advantages are increased virtualized application performance and allowance for more virtual machines per physical server. This leads to fewer virtual servers needed, lowered hardware acquisition and licensing costs, and reduced I/O demands on the shared storage system. Finally, IT benefits by smaller data center footprints associated with the applications, resulting in lowered operating expenses for power and cooling.
IT managers virtualizing their server environments have faced what storage companies call the "I/O blender" effect caused by virtualized applications slowing host computer access to storage. Even well-behaved sequential I/O applications (such as a backup job) become highly randomized, limiting access once multiple virtual machines are running on a physical server, let alone multiple physical servers running a large number of virtualized workloads.
A write-through read cache is a well-proven way to address this problem. Simply put, data that is frequently accessed by the virtual machines will be held on the high-speed flash drive. The data can be migrated out if the data become less accessed, or "cooled," without any other actions occurring with the shared storage.
The Fusion PCIe drive's integration with the ioTurbine cache software (which is already well integrated with VMware at both the hypervisor and guest OS levels) improves VMware functions such as vMotion, where a virtualized workload can be moved to other physical servers for scaling, data protection, and disaster recovery.
Despite the acquisition of ioTurbine, Fusion-io remains wedded to a heavyweight driver model and minimal in-line control components on the flash drive. This means the server is responsible for low-level flash memory management functions, like wear leveling and write amplification, rather than delegating these functions to components on the PCIe drive.
The ioCache product can be viewed as another incremental step into heavy server workloads involving storage functions. Servers are becoming more and more capable of executing these storage driver functions, but whether this is the ultimate architecture is moot. The battle for enterprise dollars in this market will see increasing participants and additional collaboration, merger, and acquisition activity, as seen in SanDisk grabbing Pliant Technologies and Fusion-io snapping up ioTurbine.
Deni Connor is founding analyst for Storage Strategies NOW, an industry analyst firm that focuses on storage, virtualization, and servers. James E. Bagley of Storage Strategies NOW contributed to this story.
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