What is and what is not wasted storage capacity is subjective, depending upon your point of view and operating environment. For example, if a server is added to your environment and that server has two internal 36 gigabyte disk drives, one may consider this wasted space if you do not use those disks. Similarly, if a product provider "bundles" a disk array as part of a server acquisition, and you chose not to use that storage capacity, that may also be perceived as wasted space.
When determining what is and isn't wasted space, one must consider the following factors:
How much will it cost you to actually use the storage?
Costs include data protection (backup, mirroring and replication); provisioning; security and the associated software tools and licenses. What will your costs be in terms of capital expenditures (capex), operating expenditures (opex) and labor/manpower to utilize the storage?
Do you have a storage need that aligns itself to the type of available storage?
What are the disk drives' performance, capacity and availability characteristics?
How are you currently managing your storage?
Do you have your existing storage managed from a basic data protection standpoint including security, backup/recovery, mirroring or replication (locally or remote), DR and so forth?
Are you migrating away from server-dedicated and direct-attached storage to a shared-access networked SAN and/or NAS storage environment?
How much available storage capacity do you currently have in your environment?
Do you currently have adequate storage capacity and/or the ability to easily expand your existing storage environment? What are your storage growth needs (e.g. storage capacity plan)?
Are you evolving towards a shared, utility, on-demand, SOA, virtual, grid or similar operating environment for your servers and storage?
Do you need server independence and flexibility to support changing workloads or ability, in order to rapidly reconfigure servers for different applications and workloads?
Where are your servers and storage located?
Are the servers and storage in the same location? Do you have remote locations? What are the requirements to have the remote data protected to a secondary remote location? How much data and storage is involved?
Another thing to consider, particularly in the case of mergers, acquisitions and consolidation, is how storage technologies will co-exist in your environment. For example, are you inheriting additional storage capacity for free, only to incur support costs and software fees to utilize it? Even if the technology is compatible with what you currently have, how is it configured and being used with respect to the rest of your environment?
You may find it to be more cost-effective to upgrade your existing environment rather than incur the cost to integrate and utilize what might be perceived as extra disk space. This would involve an analysis comparing capital expenditure (capex) to acquire new technology and disposition of inherited technologies, along with operating expenses (opex) associated with conversions, relocation and data migration.
You don't have to feel like you are wasting storage capacity space by not using it, especially if the storage capacity does not meet your needs. Keep in mind the saying "nothing in life is free" and understand how your needs and requirements align with available storage capacity and total storage management costs. Assess your needs in terms of storage capacity, operating and management requirements and application service needs. Then, analyze if it is cost effective to utilize the "free storage space" or if it is more cost-effective to not use the space that might be labeled as wasted storage space later. If there is a cost associated with using the storage that outweighs the costs of adopting the storage, then the storage should not be seen as being wasted if not used.
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About the author: Greg Schulz is a senior analyst with the independent storage analysis firm The Evaluator Group Inc. In addition to being an analyst, Greg is also the author and illustrator of Resilient Storage Networks, and Greg has contributed material to Storage magazine.