Servers get a lot of attention, but successful virtualization deployments really depend on storage. Storage protects virtual machine (VM) states, retains snapshots and provides user access to shared application data. Because of these activities, availability and performance issues place great demand on a storage infrastructure. So administrators need to understand the most critical data center storage virtualization considerations.
Data center storage virtualization consideration No. 1: Storage performance
Today, administrators can select from myriad different shared storage platforms, such as iSCSI, Fibre Channel, network-attached storage and Fibre Channel over Ethernet. Each of these platforms works fine in a virtual environment but offers radically different scalability, performance, availability and capacity characteristics.
Storage performance is usually considered chief among equals because multiple VMs residing on a physical host have considerable storage bandwidth requirements. A virtualized server hosting 10 VMs, for example, needs to load all 10 VMs from storage, to periodically snapshot the current state of each VM and to provide the VM data to users.
While storage performance must keep pace with these added demands, it's imperative to select a platform that meets your firm's needs. An iSCSI storage area network (SAN), for example, may offer the characteristics necessary for a small or midsized business, but a large enterprise may require a Fibre Channel SAN.
Data center storage virtualization consideration No. 2: Integration with backup and disaster plans
Storage systems are backed up and protected with some manner of disaster recovery (DR) planning. Any new storage implementation should be fully compatible with existing backup and DR software, such as local snapshot and remote replication tools. If not, the new storage setup may force changes (and possibly introduce errors) to the existing data protection scheme or add additional tools that unnecessarily complicate data protection. Lab testing can usually confirm a storage system's compatibility.
Data center storage virtualization consideration No. 3: Ensure redundant storage access
Storage disruptions can have devastating consequences on a virtualized data center. When a traditional server is disrupted, usually one application is affected. But when a server with 10 or 20 virtualized workloads is disrupted, it affects far more business applications and users.
Therefore, in virtualized environments, redundant storage pathways must be available to storage systems, SAN (or other network) switches and the virtual servers. This setup requires redundant storage controllers on each server and storage system, along with a well-designed redundant SAN architecture. No matter which storage architecture is in place, though, routinely verifying storage availability should be part of disaster recovery testing.
Data center storage virtualization consideration No. 4: Energy-efficient storage
The energy needed to run larger-capacity and higher-performance storage systems means a larger total cost of ownership. Consider more energy-efficient storage systems, which provide more input/output operations per second and bandwidth per watt of energy for active data. Energy-efficient storage should also provide more capacity per watt for inactive (e.g., archived) data. Achieving more energy-efficient storage is usually accomplished through a combination of controller designs and disk capacity/performance tradeoffs.
Data center storage virtualization consideration No. 5: Support for advanced storage features
Some virtualization platforms can utilize storage features, such as thin provisioning and data deduplication. Generally, storage systems that natively support these features can be more effectively utilized by a virtualization platform. This kind of mutual support often simplifies a storage setup and management requirements.
Similarly, it's important that new storage systems support the migration features in the virtualization platform. It may not be possible for the virtualization engine, for example, to migrate VMs from Fibre Channel to iSCSI to a network file system. This can potentially limit a firm's storage system choices. But other virtualization platforms, such as VMware vSphere 4, can exchange VMs among all three storage protocols, which can ease your underlying storage system choice.
Stephen J. Bigelow, a senior technology writer in the Data Center and Virtualization Media Group at TechTarget Inc., has more than 15 years of technical writing experience in the PC/technology industry. He holds a bachelor of science in electrical engineering, along with CompTIA A+, Network+, Security+ and Server+ certifications, and has written hundreds of articles and more than 15 feature books on computer troubleshooting, including Bigelow's PC Hardware Desk Reference and Bigelow's PC Hardware Annoyances. Contact him at mailto:[email protected].