Storage consolidation: Weighing the pros and cons
Storage consolidation is the practice of simplifying the storage infrastructure, allowing storage administrators to increase organization of and control over their storage resources. The need for storage consolidation stems from the fact that storage needs keep growing -- as much as 100% per year in some organizations.
Most organizations struggle just to keep up with the insatiable storage demands of users and applications by continually adding disks, arrays and servers. Over time, these organizations 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 creates four problems:
- the expense of new storage;
- an increase in storage management overhead;
- potential security vulnerabilities on one or more storage platforms; and
- a strain on facilities (e.g., power and cooling).
As a consequence, storage consolidation has become a priority for many data centers.
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, which would usually be located in the data center.
Upside of storage consolidation
Storage consolidation holds out the promise of management efficiency, since there are fewer storage platforms to manage. Administrators don't need to track and maintain a multitude of servers. Heterogeneous management software allows administrators to organize and provision consolidated storage across multiple storage systems through a single control panel.
The net result: less time spent managing with fewer errors. With fewer systems to manage, there's no need to hunt for free disk space on forgotten servers, so administrators can use the available storage to a much higher degree. For example, 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, and there are fewer hardware platforms to maintain.
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 strategy that may be 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.
Downside of storage consolidation
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 performance bottleneck, which can hurt 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, reliability becomes an issue. High-availability architectures, such as trunking and failover, can ensure that storage remains accessible in the face of network or storage system problems.
Storage consolidation can complicate some data storage management. The most pressing problem during a consolidation is often 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 you're 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 choose to replicate to a duplicate NAS in another physical location.
03 Mar 2008