In boom times, IT groups are focused on helping their organizations improve revenues and profitability. Recently capital has been easy to come by, and supporting earlier implementation of projects has been more important than maximizing ROI. As the recession bites, so the emphasis shifts to minimizing capital expenditures, and maximizing the return on assets deployed (ROA).

There are two main storage virtualization strategies, homogeneous and heterogeneous. There are advantages and disadvantages to both strategies. A key question in recessionary times is where to invest scarce capital budget. In the case of virtualization, there are three issues users should consider:

1. The length of time and internal effort required to enable virtualization
2. The amount of storage that is going to be improved (i.e. exploitation potential)
3. The capital investments needed

The obvious goal in a recession is that the hard dollar savings, in terms of increased capacity utilization, outweigh the capital costs of installing the virtualized infrastructure and allow the near term deferral of new capacity.

Homogeneous storage virtualization

Homogeneous virtualization solutions are provided by 3PAR, Hitachi USP V and VM (via internal-only storage), Compellent, NetApp, Pillar and HP’s EVA line. The advantages of this approach are:

• Better ease and speed of implementation – virtualization is built in, and there is very little if any modification to be made to the storage network. Although migration of data to the new array is time consuming and requires careful planning, it is a well understood procedure within IT. Provisioning in general is significantly simpler on virtualized arrays.
• Qualification of disk drive is automatic.
• Only one component to install – There is less complexity (all the microcode is in one box), less to go wrong, and overall it is a potentially higher reliability system.
• One set of storage management software - Centralization of software allows the potential for lower storage software costs, lower training requirements and simpler storage procedures.

The disadvantages of this approach are:

• Higher capital costs - The current equipment has to be replaced.
• Vendor lock-in - Once a specific architecture has been selected there is less choice of storage solutions, and less negotiation power with the vendor on both software and hardware
• No ability to dynamically migrate data between arrays or between storage pools. This reduces the ability to optimize storage usage, reuse older storage arrays and implement tiered storage infrastructure.

Heterogeneous storage virtualization

Heterogeneous virtualization solutions are provided by IBM’s SVC, Hitachi’s USP V and VM, EMC’s Invista, Incipient's iNSP and LSI’s SVM 5. These systems differ in their network architecture approach, but to date there has been no evidence that the different architectures significantly impact storage network response time and throughput; if properly implemented any of these approaches will work satisfactorily. All the solutions are implemented on appliances with significant attention to high-availability and zero data loss of meta-data. They all provide two main functions:

1. The ability to virtualize the storage on different array types – Each vendor provides a list of qualified storage array models (and microcode levels) that have been tested. The vendors differ significantly in the range and depth of their qualification testing.
2. A set of centralized storage management functions – Again, there are significant differences in the number of functions provided, the quality of function provided and the quality of implementation.

The overall advantages of the heterogeneous approach are:

• Lower initial capital costs – Only the appliance needs to be purchased up front. The capital cost of the virtualization storage management software is usually directly related to the amount of storage that is going to be virtualized and can be implemented in stages.
• Avoiding purchase of new storage arrays – By improving the utilization of storage on existing arrays, new array purchases can be deferred.
• Dynamic migration of data between heterogeneous arrays without application interruption - This facilitates implementing a tiered storage infrastructure, maximizes the re-usability of space on storage arrays, and elongates the useful life of storage arrays. This benefit is available after the volumes have been virtualized; the initial migration of data to a virtualized appliance causes disruption to the application, and like all migrations needs to be carefully planned and implemented.
• Storage management software can be centralized – This will assist in reducing the training costs on different management software, and simplifies procedures.
• Less lock-in for disk arrays.

The disadvantages of the heterogeneous approach are:

• The virtualization appliance is an additional element in the storage network – This adds management cost and is potentially (and historically) a source of unavailability.
• Arrays need to be qualified – Each vendor has a list of array models that are qualified on its virtualization appliance, and particular attention has to be paid to microcode levels. This reduces the choice of storage arrays available.
• Significant pre-implementation effort - This is often required on the storage network infrastructure to ensure compatibility with the virtualization appliance.
• Vendor lock-in - Implementing a storage management software in the appliance widely creates significant vendor lock-in and reduces negotiation leverage on appliance software costs.

If capital budgets have been cut, heterogeneous virtualization becomes an effective strategy to help improve the utilization and functionality of installed storage. For effective implementation, CIOs and CTOs should:

• Avoid purchase or retention of storage equipment that is not on the qualification list.
• Ensure that the storage network infrastructure is adjusted and maintained to enable a heterogeneous virtualization implementation.
• Ensure that financial information of all storage assets installed (e.g., end of lease date, extension terms) are known to the virtualization implementation team, and that virtualization priorities are driven by the financial impact on IT budgets.
• Focus the initial implementation on simple storage virtualization and thin provisioning (if available) to extent the life on installed assets.
• Focus the storage management implementation on the minimum function that will allow the use of tier 2 storage as tier 1 storage and minimize the purchase of additional tier 1 arrays.
• Negotiate a provision specifying that appliance software costs will reduce in line with storage hardware prices.
• Put in place an organization that will ensure centralized selection, management and allocation of storage resources and agree with the lines of business.

Action Item: Organizations that have avoided heterogeneous storage virtualization completely will increasingly pay a price in terms of reduced efficiencies, greater complexity and less IT flexibility. While the risk of staying the course may be lower and less disruptive in the near term, CIO's should carefully weigh those risks against cost and complexity and begin to implement heterogeneous storage virtualization strategies with the objective of better utilizing installed assets to offset virtualized appliance and license costs.

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