In the future, virtualization will encompass disk drives as well as tape and optical devices.

By Roy Slicker and Jim Wheeler, Infostor

According to the Aberdeen Group consulting firm, in Boston, virtualization separates the representation of storage to the server operating system from actual physical storage. This division of physical storage devices from the logical storage space presented to users and applications turns storage into a "utility pool."

Virtualization fulfills a role for storage similar to what an operating system does for a computer system—namely, making programming and operation simpler by automating resource management "housekeeping." When this process occurs, users are said to be "viewing resources at a higher level of abstraction." As such, virtualization is the abstraction of storage. Virtualization enables end users to pool a wide range of storage technologies from different vendors—and, eventually, different formats—and to easily add capacity and automatically move data among devices, independent of operating systems or network infrastructure.

In an Aberdeen Group report, senior analyst Dan Tanner says that the potential benefits of virtualization for IT administrators include creating virtual volumes that can span multiple storage units, enabling heterogeneous "mix and match" of servers and storage devices, and enabling secure storage sharing and efficient storage utilization.

Lately, there have been more definitions of virtualization than there are storage start-ups, with an accompanying onslaught of hype. Storage area network (SAN) vendors claim that SANs are what virtualization is all about. However, current SAN solutions do not include software to handle all storage media types such as secondary storage. Most virtualization products are limited to disk subsystems; however, hard disks only address part of the storage puzzle. Storage virtualization software should encompass all device/media types to deliver on the promises of ease of use, scalability, and cost effectiveness.

Storage virtualization should include secondary storage devices such as tape and optical libraries. Secondary storage is characterized by the ability to remove the storage media (cartridges) from the device and store it away from the primary environment.

According to a variety of studies, 80% of online information is static and unused. In addition, IDC estimates that 55% of distributed storage management costs are administrative—a number that could be significantly reduced through logical consolidation of storage resources for more-effective management. If static data is migrated to lower-cost near-line or offline storage technology, IT managers could re-claim a vast amount of their current online storage investments.

Primary Data vs. Archived Data
IT organizations generally use separate systems to store frequently accessed data and infrequently accessed, or archived, data. In many cases there is a need for software to centralize access to a broad range of media types. Users want a system that can search the entire network or enterprise from a single console and map all the available storage resources into a single share point or volume.

All data is not created equal and should not be treated equally. Disk subsystems are well-suited as primary storage for a variety of applications, but there are applications where secondary storage options are the best solution. What's needed is an approach to solving the tradeoffs between capacity, access speed, and cost, while abstracting the various layers (media types) and providing a common user interface.

Users should not have to choose between media types. In fact, users generally do not care how the data is stored as long as it's readily accessible when needed. Virtualization of storage devices should provide a system that handles all categories of data (including backup) in a cost-effective way and with a single user interface.

Some users will require a "blending" (virtualization) of the various storage technologies: "Let me decide what goes where, based on my data-access requirements and my legal exposure for storing data." There is also a concern about the cost of the overall system and its effectiveness in tracking information and recovering from failures. A single media solution for all data can be a disaster if critical information is lost. The blending of media technologies would provide users with the highest levels of performance, data security, and cost-effectiveness.

Virtualization techniques under development will enable integration of the three most common storage categories: hard disks, tape, and optical.

One of the major benefits of virtualization across media types is the cost reduction associated with the various storage resources within the shared hardware and media pool. Data that is used and/or changed frequently belongs on magnetic disk because access speed is critical. However, as capacity requirements increase, storage costs can skyrocket if all data remains on non-removable media. The vast majority of data on RAID arrays is not accessed frequently, if at all. This static data can be offloaded to more cost-effective storage media, thus freeing up space on the primary storage system.

A logical consolidation of storage technologies results in fewer IT personnel to manage growing data needs, as well as a decrease in operating downtime and a reduction of lost data. Virtualization should abstract hardware devices as well as individual media types, resulting in a single view or volume for user interaction.

All the different physical storage types on the network can create a significant storage management dilemma. A single logical view of storage using virtualization techniques can streamline data access and management. Within an organization, storage devices or resources of different types can be located either in different locations or be centrally located within a controlled environment.

A virtualization solution should include the option of using any or all storage levels. Appropriate physical media types would be automatically selected through the user application. Based on parameters previously set, the location of the stored data would be transparent to users. This kind of media blending, or virtualization, will facilitate a more efficient storage network and will provide a scalable solution that is more cost-efficient to manage.

Roy Slicker is the president of Pegasus Disk Technologies (www.pegasus-ofs.com), and Jim Wheeler is a marketing consultant with the company, in San Ramon, CA.