The impact of virtual storage appliances

Software-only storage controllers running in virtual machines are an easy, economical way to get shared storage. But current products aren’t up to enterprise standards . . . yet.

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Software-only storage controllers running in virtual machines are an easy, economical way to get shared storage. But current products aren’t up to enterprise standards . . . yet.

A virtual storage appliance (VSA) is storage controller software that runs within a virtual machine (VM) turning servers into data storage systems. There are a number of them available, including Hewlett-Packard’s StorageWorks P4000 Virtual SAN Appliance Software (formerly LeftHand), which is the most widely adopted, and VMware’s recently announced vSphere Storage Appliance. The implications of VMware offering a VSA are compelling, although the immediate impact is minimal.

VSA solutions are typically positioned as small- and medium-sized business (SMB) storage because of performance limitations that draw a distinct line in the sand between VSA and hardware-based storage systems. However, the line will begin to disappear as processors and memory become even faster and cheaper. And you can count on innovations that will overcome technical limitations and improve not only performance but reliability and scalability.

Storage networks made it possible to share what was once a very expensive resource: storage. But the cost of storage has gone down significantly and data storage vendors have created a wide range of software features that have become requisite in the data center, such as snapshots and replication. We also wanted high availability to ensure that our data was always accessible.

But now all that can be achieved in the virtual data center without storage networks. If you have 10 VMs running on a single physical server then you’re sharing the storage in that server across those 10 applications. A VSA provides the snapshot and replication features without requiring an external hardware-based storage system, and it also provides high availability to another server. All this can be done today -- there are literally thousands of VSA users who have implemented that type of environment. So what changed?

Adding a product like Fusion-io’s PCIe-based solid-state storage to this environment makes things a bit more interesting. Performance tests with Fusion-io-equipped VSAs don’t reach the vendor’s touted 100,000 IOPS but can achieve approximately 30,000 IOPS, which is very respectable performance, especially for a VSA system that typically tops out at approximately 5,000 IOPS. But the main reason you go with a VSA is cost, and adding Fusion-io or any other solid-state storage will increase the price significantly. Price/performance is what matters, so combining solid-state and VSA isn’t necessarily front of mind when considering alternatives to traditional storage networks.

But the writing’s on the wall. The elements needed for a new class of VSA -- an enterprise-class VSA -- are taking shape. Enterprise-class VSA requires new software, a purpose-built architecture and physical servers with new storage-specific designs to overcome the limitations of today’s VSA products. This last point is an important one: optimizing servers to support storage systems doesn’t mean building a storage system but rather having the proper reliability and availability that external storage arrays provide.

There are some applications that still aren’t being virtualized because of performance limitations. Many of these are high-performance database applications that can’t afford the inherent latency of virtualization. But an enterprise VSA would be architected to enable even the most performance-starved applications to be virtualized.

Ultimately, VSAs could spell doom for networked storage. Not only could it happen, but it should happen. Enterprise VSA would exponentially drive down costs, improve manageability and result in landscape-changing business enablement. But it will take time because of technology incumbency, lack of awareness, internal politics and the fact that enterprise VSA is just a good idea. And existing VSA solutions will need major architectural changes to evolve into enterprise VSA.

This doesn’t mean storage goes away. On the contrary, it’s storage technology, expertise and experience that will make the difference. If storage system vendors cling to the legacy of the physical data center, they run the great risk of overlooking the value of this new storage concept. EMC has taken a small step toward this approach with its new PCIe card, but it’s modest at best.

The server vendors are well positioned because they now own advanced storage technologies as well as server platforms. But they still seem less inclined to innovate. VMware has taken an important step with its VSA, but it’s not clear if they have a grand vision of merging virtual server and storage into a common stack. And even with their tight connection to EMC, VMware has very little storage DNA. Enterprise VSA is up for grabs and the vendor that gets it right will be the next big player.

BIO: Tony Asaro is senior analyst and founder of Voices of IT.

This was first published in September 2011

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