BY DAVE SIMPSON
As might be expected with a new technology, vendor hype seems to be preceding end-user adoption by more than a year in the storage virtualization space. Despite the noise and obvious potential advantages, storage integrators report relatively little demand for virtualization among end users.
"There's not a lot of demand for virtualization now, but users are starting to ask for it because they know how quickly their storage is growing, and they have to figure out how to manage it," says Mike Cush, chief technology officer at Adexis (formerly Cranel Storage).
"At our network storage seminars, approximately 80% of the end-user attendees haven't heard of virtualization, or at least don't know what it is," reports Bill Pinkerton, director of storage marketing at Pioneer-Standard. "There's a tremendous amount of interest, when we bring it up, but there's not a lot of knowledge or awareness."
Among the reasons why virtualization has not met with more widespread adoption, integrators cite the following:
- The adoption rate of storage area networks (SANs) is still relatively low, and although virtualization is not necessarily tied to SANs, that's where its benefits really shine. Integrators expect adoption of virtualization to pick up next year in lock step with SAN deployments;
- Most SANs are homogeneous (e.g., the servers and disk arrays were purchased from a single vendor), and those SANs are much easier to manage than heterogeneous SANs; and
- Lack of awareness among end users and confusion about what virtualization actually is.
"Virtualization separates the representation of storage to the server operating system from actual physical storage," according to Dan Tanner, senior analyst with the Aberdeen Group consulting firm, in Boston. That's a good base definition, but to many vendors, virtualization includes a lot more, leading to confusion among users.
Starting with that base definition, Adexis' Cush identifies five storage virtualization architectures, or approaches (with vendor examples in parentheses):
- Host-based (Veritas' Volume Manager);
- Host bus adapter-based (Troika);
- Storage subsystem-based (most disk array vendors);
- In-band (DataCore, Vicom, and XIO tech); and
- Out-of-band (StoreAge).
Other virtualization vendors include Compaq, DataDirect Networks, Falcon Stor, IBM/Tivoli, and StorageApps (recently acquired by Hewlett-Packard).
"Users have been doing virtualization at the host and HBA level for a long time," says Cush, "but that doesn't give you all the functionality that virtualization promises."
Scott Robinson, chief technology officer at Datalink, agrees with Cush: "If you exclude virtualization-like functionality such as a volume manager or LUN mapping, we haven't seen a lot of end-user demand for virtualization," says Robinson. "Users aren't necessarily looking for virtualization: That's just one piece of their bigger management puzzle."
Robinson says that some end users may want to consider virtualization solutions not so much for the base virtualization functionality, but for the "gravy" applications that some vendors offer as options, such as remote mirroring, replication, snapshots, and IP storage.
But in the end, the biggest gating factor to end-user acceptance of virtualization is still their reluctance to buy into the SAN concept. "Our biggest challenge is explaining to end users why they need a SAN; then, you explain why they need virtualization," says Ron Babich, executive vice president of sales and marketing at SanOne.
However, Babich says that approximately 75% of SanOne's SAN installations do use virtualization. Unlike most other third-party storage integrators, SanOne has an OEM relationship with a virtualization vendor: StoreAge. SanOne added a GUI layer to the StoreAge product and resells it under the name "Dynamic Allocation Manager" (although the company was in the process of changing the name of the product at press time).
Despite the relative lack of end-user adoption of virtualization, recent moves by some consulting firms and integrators indicate that interest may be picking up. For example, at last month's Storage Networking World conference, Imation introduced a storage virtualization assessment and design service. Imation, which has no reseller ties to any virtualization vendor, claims to have a matrix that can help users map their requirements to the best storage virtualization approach.
Mike Hogan, general manager of Imation's Storage Professional Services organization, underscores the importance of making the right choice among the various virtualization options: "Virtualization is a very strategic decision, and if you make the wrong decision you really paint yourself into a corner, and getting out of it is tough."
All third-party integrators agree that virtualization offers a number of potential benefits to end users, assuming you have a SAN that's large and/or heterogeneous.
"The key advantage of virtualization is that it adds a layer of abstraction between the storage and the servers," says Datalink's Robinson. "Most users have a lot of different storage devices and servers, and they don't want to have to learn how to manage them all individually."
SanOne's Babich says that the top three end-user benefits of virtualization are
- Centralized management and ease of management of heterogeneous platforms;
- A significant reduction in interoperability problems; and
- Maximization of disk space utilization.
"What's driving the need for virtualization is the mass quantities of storage and the fact that users don't want to be tied to a single vendor," says Imation's Hogan. "Users want to standardize and 'commoditize' their back-end storage, and virtualization allows them to do that."
Once you've determined the need for virtualization, you'll have to evaluate the various options. If you include volume managers in the definition of virtualization, then analysts say that Veritas is the hands-down market share leader because of the popularity of its Volume Manager software.
Beyond that, the market for virtualization products is dominated by relatively small vendors, although large vendors such as Compaq, EMC, and IBM/Tivoli are delivering pieces of their virtualization strategies. Hewlett-Packard bought its way into the virtualization market earlier this year with the $350 million acquisition of StorageApps, a move that is expected to raise the visibility of virtualization in the end-user community. (Dell also resells the StorageApps product, although that may change in light of HP's acquisitions.)
Controversy lingers: In-band vs. out-of-band
One issue is still debated: Should virtualization occur in-band (e.g., via an appliance in the data path between the servers and storage devices) or out-of-band (outside the data path)? So far, the only vendor delivering an out-of-band virtualization solution is StoreAge.
Imation's Hogan echoes the opinions of other integrators: "In-band approaches face the challenge of scalability [because the appliance is in the data path], and you may have performance degradation, but the advantage is that you don't have to put software on all the participating hosts, and it's fairly simple."
Some in-band virtualization vendors counter the potential performance degradation problem with large amounts of cache. (DataCore, for one, actually claims to be able to increase performance.) But large amounts of cache significantly increase costs, which is still one of the biggest gating factors to end-user adoption of SANs. Also, unless you implement in-band virtualization appliances in expensive, redundant fail-over pairs, the appliance represents a potential single point of failure.
Another advantage of in-band approaches "is that they give you more versatility on the back-end in terms of replication, snapshots, and other functions," says Danny Marmol, a senior systems engineer at ITIS Services.
In addition, Marmol agrees that in-band appliances can create bottlenecks. (ITIS resells and integrates FalconStor's IPStor and Veritas' SERVPoint products.)
"The main drawback to out-of-band approaches," according to Imation's Hogan, "is that you have to put software drivers on all the hosts. It may require custom development at the operating system level, but it has great scalability."
"The in-band, or symmetrical, approach seems to be 'winning' in the marketplace," says Datalink's Robinson, "but users would have to have a lot of confidence in the in-band solution provider because the appliance sits in the data path. That's a big hurdle for the smaller vendors."
Another hurdle for both vendors and users is that there are no standards for virtualization, and none are on the horizon, although the topic is under discussion in the Storage Networking Industry Association. (For more information on the standards problem, see "Storage virtualization needs standards," p. 58.)
As the concept of virtualization gains traction in the end-user community, expect the larger vendors to enter the market in a big way-and that may include switch vendors. Brocade, for example, is expected to enable virtualization in its upcoming 12000 fabric switches.
"All of the big vendors are trying to get a piece of the SAN management pie," says Adexis' Cush. "It's like a pack of screaming dogs with food in the room."