Take the word virtualization as applied to storage. The Wikibon definition says that block storage virtualization “… breaks the physical connection between the LUN (server side) and the physical volume (array side); the virtualization engine keeps track of (maps) the connection between the LUN and the virtual volume (as the server sees it), and the connection between the virtual volume and the physical volume (as the array sees it).” This applies to storage virtualization as implemented by IBM’s SVC, Hitachi’s USP products and recently EMC with Invista. All allow, for example, data to be migrated without disruption within an array or from one array to another, and allow a full implementation of tiered storage. This can be best described as non-disruptive heterogeneous virtualization. This is excellent strategic fit for large data centers with multiple arrays, where avoiding disruption of applications is a high priority. One Wikibon member uses this to wean people off traditional tier-1 storage, with the promise that if the performance is not adequate with a tier-2 array, it can be seamlessly and non-disruptively migrated back to tier-1 storage.
NetApp's FAS (and 3PAR's InServ) storage systems claim to have virtualization as well. And they are right – they both have strong virtual architectures that allow the virtual mapping of volumes within a single array. This allows for high utilization and simplified performance tuning within that array. This is best described as homogeneous virtualization and is an excellent strategic fit for installations with fewer arrays where non-disruptive migration is not the most important issue, or as a solution for a specific storage pool supporting (say) virtualized servers.
And then there is NetApp's V-Series, which is both a NAS gateway and a SAN virtualization platform. It is heterogeneous virtualization in the sense that the storage can be provided from qualified storage arrays from other vendors (such as the EMC CX array). Other than RAID, all functionality for the attached storage is provided by the V-series appliance. It provides great connectivity and the ability to extend the life of existing storage arrays, but not non-disruptive migration of block-based storage.
Action Item: It cannot be assumed that technologies such as virtualization and thin provisioning will be implemented or integrated the same way by vendors. Humpty Dumpty in Lewis Caroll’s “Through the Looking Glass” asks “which is to be master.” The business requirement is to be master; choose the best strategic fit of the technology to those business requirements and priorities. If you are talking to NetApp as a general purpose storage supplier for the first time, invest in developing a dictionary to translate NetApp storage-speak. It will be worth the effort.
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