Storage in utility computing: 7 critical questions for IT

Computer Technology Review, March, 2004 by E.P. Komarla

The principal focal point of interoperability is the interface between the infrastructure of the utility and the infrastructure of the customer. Utilities need to provide managed storage services to customers across a wide spectrum of computing platforms. Today's approach to manageability involves separate solutions for compute, storage and network resources, each based on different standards. A practical computing utility model for storage will require a unified framework for the management of all of the entities within a data center.

The manageability standard must comprehend all of the following functions:

Configuration: This means that features, servers and software can be added or changed without bringing the system down. Other parts of the system must be able to recognize the changes as they occur and adapt accordingly, with minimal human intervention.

Self-healing: The system must be able to recognize a failed component, take it off line and repair or replace it. For example, if a file becomes corrupted, the system can locate a copy on a mirror site and replace the damaged file. If a server goes down, the system automatically routes traffic to a backup server.

Protection: The system monitors who is accessing resources. It blocks and reports any unauthorized access.

Optimization: The system constantly monitors and tunes storage, databases, networks and server configurations for peak performance.

Fault Tolerance

The utility computing storage infrastructure must have extremely high aggregate fault tolerance, even when individual components have lower fault tolerance. This is achieved through redundancy in subsystems and components, and failover-awareness throughout the software stack, including applications, middleware and operating systems. The failover mechanisms must be transparent to users and applications. It is one thing to provide fault tolerance within a relatively controllable enterprise-computing infrastructure. It is quite another to do so in a utility environment which must meet the requirements of multiple customers who may have a variety of service level agreements and QoS expectations.

In enterprise deployments, fault tolerance is achieved in a variety of ways, ranging from RAID and local copying to replication of data at mirrored sites connected by a dedicated link. In the ideal scenario, in the event of failure at one site, storage services are maintained by the mirror site with no perceptible interruption. Utilities will need to provide their customers with a range of reliability and availability options that can be tailored to each customer's requirements. When evaluating a utility computing vendor, companies must be highly aware that off-the-shelf solutions that may be adequate for enterprise use may not work within the relatively more complex infrastructure of a utility.

Provisioning: Allocation and Assignment

Which storage devices will be used before a particular job is started? How much will each be used? The system must be capable of adding or deleting storage or computing resources, as needed, using front-end software tools. When a new storage entity is added to the pool, it must be discovered by the system and provisioned with the right firmware and operating environment. This capability enables a bare-bones storage entity to be discovered and provisioned from a central console.