Review: Flash your way to better VMware performance

Admins will have no trouble analyzing the health and performance of the flash cluster. The PernixData management console integrates into vCenter Server. Find the Performance section under the PernixData tab in vCenter, and a wide range of customizable charts and graphs are available, including virtual machine IOPS, virtual machine latency, and cache hit rate and eviction.

The hit rate and eviction rate charts are the keys to ensuring the flash cluster is sized correctly for the number of running VMs. Hit rate is a measure of how many I/O operations are being served by the server-side flash as opposed to being served by the SAN. A hit rate of 100 percent tells us our flash cluster is sized correctly for the running VMs in our environment. A real-world hit rate of 85 percent is typical and reasonable.

Eviction rate is a measure of how much data is being flushed from the cache to make room for new data. Let's say you have 100GB of server-side flash for two VMs, each with a size of 75GB. Because only 100GB of cache are available and the VMs have a total working size of 150GB, at some point older data will have to be cleared from the cache to accommodate new data. The percentage of data being removed from the cache is the eviction rate. In a perfect world, the eviction rate would be 0 percent, indicating that the server-side flash was large enough to satisfy all the reads and writes for both VMs.

PernixData FVP is a great product for any VMware server farm bogged down by SAN bottlenecks. It installs cleanly into the hypervisor, works with heterogeneous flash devices, and scales as the vSphere cluster grows. Best of all, it provides true write-back capabilities. And because PernixData FVP doesn't restrict vMotion and other VMware services, there really isn't a scenario where its distributed flash cache doesn't make sense to improve VM and SAN performance. 

This article, "Review: Flash your way to better VMware performance," was originally published at InfoWorld.com. Follow the latest developments in virtualization, data center, and cloud computing at InfoWorld.com. For the latest business technology news, follow InfoWorld.com on Twitter.