Most enterprise IT organizations have dabbled in server virtualization, which requires high storage availability and performance. This part of deployment can be challenging, according to a Forrester study.

The report, “Storage Choices for Virtual Server Environments,” reveals that most businesses use VMware, with a small portion choosing Microsoft Virtual Server 2005, Hyper-V, or Citrix XenServer. The applications most likely to be virtualized include Web, commercial off-the-shelf, and infrastructure apps.

IT leaders interviewed for the study identify their top storage struggles in a virtual server environment. Forrester finds the following:

* Maintaining high performance is tricky. There are lots of moving parts. Work with a vendor to fully test possible configurations in a lab environment that closely resembles production workloads.

* Server virtualization compounds backup complexity. As the ratio of virtual machines to physical hosts grows, backing up new data within defined maintenance windows is difficult.

* Server virtualization can decrease capacity utilization. Many organizations find it difficult to create and keep a consistent, efficient process for allocating storage to virtual servers. It is here where thin provisioning helps, though not many companies take advantage of this capability. Forrester recommends seeking storage solutions that offer thin provisioning.

Overall, companies tend to stick with the big storage vendors for virtual server environments – companies such as EMC, Hitachi Data Systems, HP, IBM and NetApp. IT leaders tend to prefer a single storage vendor. Not surprisingly, Fibre Channel is the most popular storage protocol for virtual server deployments, though iSCSI is popular in smaller firms.

For those considering new deployments, Forrester suggests tapping the flexibility and cost advantages of iSCSI and NFS. Also, give a lot of thought to your backup and restore conditions. Seek out backup designed specifically for virtual environments and look for snapshot and replication capabilities.

Amy Schurr is the former managing features editor of Network World.