Storage consolidation: Weighing the pros and cons

Over time, these organizations eventually suffer the effect of storage sprawl, where data is stored on disks and systems in the data center, throughout the organization and even across the world by virtue of remote offices and mobile users. This proliferation of storage assets presents three main problems: the expense of new storage, an increase in storage management overhead and a strain on facilities (e.g., power and cooling). As a consequence, storage consolidation has become a priority for many data centers.

Any storage consolidation initiative should start with an evaluation of the advantages and disadvantages. Most storage consolidation efforts involve replacing multiple disparate storage platforms with a single storage resource. For example, an organization with 400 storage servers spread out over the enterprise could consolidate its storage into a single storage area network (SAN) or a network attached storage (NAS) system, one typically located in the data center.

Storage consolidation: The upside

Storage consolidation holds out the promise of management efficiency. There are fewer storage platforms to manage. Administrators don't need to track and maintain a multitude of servers. Heterogeneous management software often allows administrators to organize and provision consolidated storage through a single control panel.

The net result is less time spent managing with fewer errors. With fewer systems to manage, there's no need to hunt for free disk space on long-forgotten servers, so administrators can use the available storage to a much higher percentage. For example, the storage on distributed servers rarely sees more then 50% utilization; consolidated storage utilization can easily exceed 80%. Recovering this forgotten storage can result in significant cost savings.

These simplifications also make it easier to "see" the storage in order to generate utilization reports and even predict future storage needs. Such storage resource management (SRM) in turn allows organizations to save money by budgeting storage acquisitions more accurately. It also helps them take advantage of falling storage costs over time -- a tactic that analysts suggest is more cost-efficient than making bulk disk purchases today. Finally, reducing the number of storage systems often minimizes power and cooling demands on data center facilities.

Storage consolidation: The pitfalls

Storage consolidation also has downsides, such as network performance. With storage concentrated in a few centrally located devices, all of the storage traffic will pass across the same network connections. This can lead to a serious performance bottleneck, which can impact application performance and user service levels. Therefore, it's important to evaluate the network architecture early in the storage consolidation process and accommodate any changes or upgrades needed to ease potential bottlenecks.

With more users relying on fewer storage systems, experts also point to potential reliability issues and recommend the use of high-availability architectures, such as trunking and failover, to ensure that storage remains accessible in the face of network or storage system problems.

Storage consolidation can also further complicate data storage management. The most immediate problem during a consolidation is data migration, since the data from a myriad of disparate systems must be moved to the new storage system(s). In many cases, migration must occur with little (if any) actual downtime for applications. Bottom line: Be sure that new storage systems offer adequate data migration tools.

Post-deployment, you'll need to address data backup and disaster recovery processes. Backup windows may increase dramatically when backing up a large concentration of data, and this may require disk-based backup techniques such as virtual tape libraries or disk-to-disk. Some users who consolidate to a single large NAS will replicate to a duplicate NAS in another physical location.