Storage Hypervisors Vs. Software Defined Storage

The IT industry is an incubator for new technology and new buzzwords. The interest around software defined networking (SDN) has given rise to the term software defined data center (SDDC), and vendors are also now talking about software-defined storage (SDS). Software-defined storage includes such concepts as policy-driven storage provisioning and the use of virtual volumes, in which the physical hardware is separated from how it appears logically to the user.

Invoking the dictum that there is nothing new under the sun, SDS sounds suspiciously like storage virtualization. There are multiple paths to storage virtualization, one of which is the storage hypervisor. Let’s look at the connection between SDS and storage hypervisors.

Storage Hypervisors in a Nutshell

A storage hypervisor is a supervisory program that manages multiple pools of storage as virtual resources. It treats all the storage hardware it manages as generic, even though that hardware includes dissimilar and incompatible platforms. To do this, a storage hypervisor must understand the performance, capacity and other service characteristics of underlying storage, whether that represents the physical hardware, such as solid-state disks or hard disks; or the storage architecture, such as storage-area network (SAN), network-attached storage (NAS) or direct-attached storage (DAS). I’ve written about three vendors that offer storage hypervisors: IBM,Virstoand DataCore.

A storage hypervisor can also accept new devices (such as a new array) or the replacement of part or all of an existing pool of storage resources without causing business disruption. That means that it instantiates the characteristics and capabilities of what it gains and recognizes what it is losing.

In other words, a storage hypervisor is more than just a combination of a storage “supervisor” and storage virtualization features. It represents a higher level of software intelligence that controls device-level storage controllers, disk arrays and virtualization middleware. It also provisions storage, provides services such as snapshots and replication, and manages policy-driven service levels. The storage hypervisor provides the technology on which software-defined storage can be built.

Why use a storage hypervisor? Proponents cite a number of benefits, including better utilization of existing storage, improved productivity of administrators, and better performance and availability.

Two Obstacles

IT organizations have long touted the use of integrated hardware and software to solve business problems, but, even though considerable progress has been made over the years, IT is still in a physician-heal-thyself mode in regard to using hardware and software. This, in essence, is what concepts such as SDS and the cloud are really all about.

Storage hypervisors are one means of bringing true management to one of the key components of the information infrastructure--namely, storage. But storage hypervisor and storage virtualization vendors (as well as those companies that sell other advanced software to create and/or manage SDDC and SDN environments) face two big challenges. The first is that IT is of two minds regarding change. While IT is willing to make dramatic changes when necessary (such as a clear and strong proof that change would be beneficial), IT has to be shown that changes are necessary (as switching costs are not only measured in dollar terms, but also in risk management terms).

The second challenge is how to effectively get one’s hands around a wide range of computing functionalities. IT tends to be divided into narrow domain expertise silos, and achieving the benefits from advanced software may very well require it being adopted broadly within an organization, requiring a fairly steep learning curve by numerous individuals and groups. Much of the automation enabled by a storage hypervisor aims to remove that obstacle.