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Virtual SAN is a software technology that delivers shared storage to servers without the need for a physical SAN. This is done by pooling together all the server-side storage resources and presenting the pool to the operating system or hypervisor as shared storage.
Virtual SAN software can create a high-performance, server-based SAN without using any external storage arrays, switches, HBAs , and other fabric components like a physical SAN. Using virtual SANs can also lower overall costs by utilizing existing solid-state storage in servers rather than purchasing new hardware.
This shared storage pool can be created within a single server, server cluster, or part of a remote office infrastructure with many remote offices around the world. Virtual SANs are meant to be a scale-out architecture that scales storage with compute as server nodes are added to a cluster.
Virtual SAN offers availability, reliability, efficiency
Virtual SAN software can enable greater availability and reliability and make effective use of server-side storage. It also enables non-disruptive data movement, which in turn enables simplified management and better utilization of storage capacity. Virtual SAN vendors also claim that there are no special training or certifications to deploy and maintain a virtual SAN.
Today, virtual SAN software, such as VMware VSAN, StorMagic SvSAN, Datacore SANsymphony Virtual SAN and EMC ScaleIO, has extended support to solid-state storage. This allows users to create a high-performance, persistent solid-state tier of storage for critical applications that require low response times.
Both SSDs and PCIe flash cards can be pooled to put high-performance storage close to an application for lower latency. Some vendors have gone so far as to add auto-tiering which allows for hot data to stay in the solid-state tier for better performance while less frequently accessed data can be stored on traditional disk drives.
Virtual SANs are growing in popularity as storage and virtual infrastructure administrators seek ways to lower storage costs while providing the high performance, availability and reliability expected from storage networks. For some, virtual SANs are a key piece of technology that can enable storage IT departments to build a reliable infrastructure with solid-state storage that is scalable at a lower cost. Virtual SAN vendors claim their products cost 50% to 80% less than deploying a physical SAN.
Virtual SAN offers an alternative to solid-state arrays
Solid-state arrays do have their place; this does not replace their value, but virtual SANs can be an alternative in some infrastructures.
Virtual SANs are particularly effective for businesses that have many remote locations. Virtual SAN products allow for remote replication and centralize management of thousands of sites. This means that solid-state storage sitting in those remote servers can now be used as a high-performance shared storage pool for whichever location needs performance at any given time. This would be very expensive and difficult to deploy and manage from a physical SAN.
On the other hand, remote operations of this type may add latency to I/O operations that can result in reduced transaction processing. These considerations have to be weighed. Also, this does not mean vendor lock-in is eliminated. It just moves the lock-in to the virtual SAN software.
It is important to remember that virtual SAN software is a means to an end; virtualizing the SAN itself should not be the goal. That is, virtual SAN software should be used as a tool to enable other goals, such as providing highly reliable storage or lowering costs.
About the author:
Leah Schoeb is a senior partner at Boulder, Colo.-based Evaluator Group.
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