Finally, the pace of change has accelerated to the point where any infrastructure put in place must either be flexible enough to address both current and anticipated future needs, or it must be rebuilt time after time as the needs of the organization change. Applications, databases, and the computers that host them are being re-engineered and redeployed. Ultimately, the content itself is the center around which the changing infrastructure revolves. Information storage architectures are tied to those applications, databases, and computers; and therefore, must also be flexible enough to enable the re-engineering and re-deployment of an organization's assets.
Result
At its simplest level, the factors described above result in two "situations" that ultimately relate to issues of distance and connectivity. These situations are:
* Captive hosts
`Captive storage' describes the situation where all connections into a storage array are fully utilized, but the array itself has available capacity. This typically results from situations where each host has small information storage requirements, the disk drive density increases beyond the needs of the number of hosts that can connect to an array, or when the array has relatively few available connections. As an example, consider consolidating NT application and file serving information on a storage array with 32 available SCSI connections and an available capacity of 9TB of protected storage. If the typical NT server requires 50 GB of storage and you could connect 32 servers, you would utilize 1.6 TB or less than 20% of the available capacity of the array. This results in a higher than optimal cost per unit of storage (because of the fixed costs associated with the array and storage software). Further, that array is now unavailable to the next server, forcing it to go onto a secand array making it harder to pass information back and forth with the other servers on the first array and increasing the effort it takes to manage the environment. `Captive hosts' describes the reverse situation as captive storage. Essentially, the storage requirements of the hosts connected to a storage array grow to exceed the capacity of that array. This means that an additional array must be deployed and the hosts and information redeployed and balanced across the two arrays. This involves substantial effort and downtime associated with planning, executing, and testing the migration of the hosts and storage from the original array to the new configuretion. Additionally, you end up underutilizing available storage assets if there is available capacity elsewhere in the infrastructure that is impractical to use due to distance or connectivity requirements between host and storage.
Traditional information storage infrastructures are intimately coupled with the application infrastructure (including processors, software, etc.) they support. What this means is that when you need to make a change in the application infrastructure, the information infrastructure is affected as well (and visa versa). For example, consolidating a number of applications onto a single host platform would involve migration of applications as well as configuring and implementing the new (consolidated) host platform. In addition to this application infrastructure change, the storage infrastructure must be revisited to ensure-that this new single host has access to the combined information of all the original applications. Ultimately, this coupling makes it more difficult for organizations to be flexible and to rapidly deploy, change, or remove applications to meet their evolving needs.