Storage virtualization has been out for at least 5 years now and one can see more and more vendors offering products in this space. I have written before about storage virtualization in “Virtualization: Tales from the Trenches” article and I would say little has changed since then but it’s time for a refresher.
Storage virtualization differs from file or server virtualization by focusing only on FC storage domain. Unlike server virtualization there is no need to change host operating environments to support most storage virtualization products.
As an aside, there may be some requirement for iSCSI storage virtualization but to date I haven’t seen much emphasis on this. Some of the products listed below may support iSCSI frontends for FC backend storage subsystems but I am unaware of any that can support FC or iSCSI frontend for iSCSI backend storage.
I can think of at least the following storage virtualization products – EMC Invista, FalconStor IPStor, HDS USP-V, IBM SVC, and NetApp ONTAP. There are more than just these but they have the lion’s share of installations, Most of these products offer similar capabilities:
- Ability to non-disruptively migrate data from one storage subsystem to another. This can be used to help ease technology obsolescence by online migrating data from an old subsystem to a new subsystem. There are some tools and/or services on the market which can help automate this process but storage virtualization trumps them all in that it can help tech refresh as well as provide other services.
- Ability to better support multiple storage tiers by migrating data from one storage tier to another. Non-disruptive data migration can also ease implementation of multiple storage tiers such as slow/high capacity disk, fast/low capacity disk and SSD storage within one storage environment. Some high end subsystems can do this with multiple storage tiers within one subsystems, but only storage virtualization can do this across storage subsystems.
- Ability to aggregate heterogeneous storage subsystems under one storage management environment. The other major characteristic of most storage virtualization products is that they support multiple vendor storage subsystems under one storage cluster. This can be very valuable in multi-vendor shops by providing a single management interface to provision and administer all storage under a single storage virtualization environment.
- Ability to scale out rather than just scale up storage performance. By aggregating storage subsystems into a single storage cluster one can add storage performance by simple adding more storage virtualization cluster nodes. Not every storage virtualization system supports multiple cluster nodes but those that do offer another dimension to storage subsystem performance.
- Ability to apply high-end functionality to low-end storage. This takes many forms not the least of which is sophisticated caching, point-in-time copies and data replication or mirroring capabilities typically found only in higher end storage subsystems. Such capabilities can be supplied to any and all storage underneath the storage virtualization environment and can make storage much easier to use effectively.
There are potential downsides to storage virtualization as well, not the least of which is lock-in but this may be somewhat of a red-herring. Most storage virtualization products make it easy to migrate storage into the virtualization environment. Some of these products also make it relatively easy to migrate storage out of their environment as well. This is more complex because data that was once on this storage could be almost anywhere in the current virtualized storage subsystems and would need to be re-constituted back in one piece on the storage being exported.
The other reason for lock-in is that the functionality provided by storage virtualization makes it harder to remove. But it would probably be more correct to say “once you virtualize storage you never want to go back”. Many customers I talk with that have had a good initial experience with storage virtualization want to do it again, whenever given the chance.