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10 tips for managing storage for virtual servers and virtual desktops | Eric Siebert | Oct 2010

Server virtualization and virtual desktops can make configuring and managing storage systems a lot tougher. These 10 tips can help ease some of the stress caused by managing storage in a virtual environment.

Server and desktop virtualization have provided relatively easy ways to consolidate and conserve, allowing a reduction in physical systems. But these technologies have also introduced problems for data storage managers who need to effectively configure their storage resources to meet the needs of a consolidated infrastructure.

Server virtualization typically concentrates the workloads of many servers onto a few shared storage devices, often creating bottlenecks as many virtual machines (VMs) compete for storage resources. With desktop virtualization this concentration becomes even denser as many more desktops are typically running on a single host. As a result, managing storage in a virtual environment is an ongoing challenge that usually requires the combined efforts of desktop, server, virtualization and storage administrators to ensure that virtualized servers and desktops perform well.  Here are 10 tips to help you better manager your storage in virtual environments:

#1 Know your storage workloads. Virtual desktop workloads are very different from virtual server workloads, and the workloads imposed by individual desktops and servers can also vary dramatically. Blindly placing VMs on hosts without regard for their disk I/O usage can create instant resource bottlenecks.

You should have a general idea of how much disk I/O a VM will generate based on the applications and workloads it will host. Therefore, you should try to balance high disk I/O VMs among both physical hosts and data resources. If you have too many VMs with high disk I/O on a single host it can overwhelm the host’s storage controller; likewise, having too many high disk I/O VMs accessing a single storage system or LUN may also create a performance bottleneck. Even if you have a good idea of your virtual machine’s disk I/O workloads, it’s still a good idea to use performance monitoring tools to get detailed statistics such as average and peak usage.

And don’t forget that VMs are usually mobile and may not always be on the same host; they may be moved to another physical host using technologies like VMware VMotion. Having a group of busy Exchange servers ending up on the same host could bring the disk subsystem to its knees. If you’re using VMware’s Distributed Resource Scheduler (DRS) to balance workloads among hosts, keep in mind that it doesn’t take VM disk I/O usage into account, it only balances based on CPU and memory usage. To compensate for that, use DRS rules that will always keep specific virtual machines on different hosts.