Traditionally storage systems and other storage related services have been delivered as customized systems. This was done to maintain performance and to reduce support costs to the manufacturers. As server technology continues to increase in performance, the concept of providing storage services as a standalone application installed on your own server hardware is becoming increasingly popular. Now with virtualization the storage as an application concept is being applied to virtual machines.There are many techniques to running storage applications as virtual machines and this series will look at those and provide some information on what is best for your environment. The first decision is of course to decide how you want to apply storage in your environment. The traditional method of a stand alone customized storage system will still have merit for a long time. Certain environments are just going to need the high performance and high reliability of these systems.

For a growing number of environments, off the shelf standard storage hardware is going to offer more than enough performance. As we discuss in our article "Virtual Storage Infrastructure", with more powerful servers storage software can take center stage. In fact some vendors claim that they can out-perform specialized systems with standard hardware. Companies like StarWind Software, DataCore, Nexenta and FalconStor all can convert a group of servers into a highly available storage server. This does still require a storage network to be installed and stand alone servers be used, but it does provide a predictability of performance.

The other option is to leverage the server virtualization environment and use it to provide a virtual appliance to run various storage services. The above companies as well as HP's Lefthand Networks and EMC's Celerra and Avamar products can run as virtual machines. The advantage is that these storage services can be provided without using an additional piece of server hardware and they provide the manufacturer with a somewhat consistent hardware configuration, although virtual, to be able to baseline their support efforts against.

In most cases these virtual appliances will use the locally attached storage of a particular host and in others they will aggregate the storage across multiple hosts within the server virtualization cluster. As we walk through the various offerings we will detail how the storage is utilized and accessed as well as how high availability is achieved.

The consideration with storage as a virtual appliance is what will the impact on the other virtual machines be and what will the impact on storage performance be? Clearly this style of achieving shared storage and advanced storage services is not for everyone. Again however, if you have modest workloads or have a fair amount of excess compute capacity in your server virtualization cluster it is certainly something that should be considered.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.