Data storage capacity planning can be a complicated and time-consuming operation, but it doesn't have to be. You can get a useful estimate of your data storage requirements by gathering some statistics and asking a few simple questions. Small- to medium-sized businesses (SMBs) should ask themselves these five questions to help them get started with their data storage capacity planning:
What data storage capacity planning tools do you have to help you?
SMBs have a few data storage capacity planning tools at their hands already. For example, you can use PerfMon, a performance monitoring utility that comes with Windows that can show total disk space and the amount of disk space being used. Another basic tool is to use Excel and make up a spreadsheet. However, the process goes more smoothly and with finer granularity if you have specialized tools to help. Besides PerfMon and Excel, you may also have other capacity planning tools. For instance, if you have storage management software from your storage system vendor, you already have a module that tracks the growth of your storage systems and can provide a growth rate for each of them.
There are also specialized capacity calculators, and there are online versions available free from storage vendors such as Dell's Data Center Capacity Planner.
For more detailed estimates, you can use a specialized program like Aptare StorageConsole Capacity Manager or Uptime software's capacity management tool. Uptime's product costs $695 per physical server.
What are your present data storage requirements?
Remember that you're planning for the total storage capacity needed, not just the amount your system reports as available. For example, if you're using RAID 10, you need twice as much disk space as you have data to allow for RAID 10's mirroring. (By contrast, RAID 5 uses 33% or less additional space for redundancy. How much redundancy depends on the number of disks in the array. A three-disk RAID 5 array has 33% redundancy. A nine-disk array only has 11%.)
How fast are your data storage needs growing?
The next step to take in capacity planning is to figure out your data storage growth rate. This can be done on a monthly or on an annualized basis. As mentioned earlier, you can do capacity planning without specialized tools. In that case, you have to figure out your storage growth manually.
The lowest cost method to figure out your growth rate is to consult your log files and see how much your storage capacity usage is increasing monthly. A more sophisticated method is to use the numbers from the planning module of your storage management software or other specialized software. Capacity planning software will also give you these numbers.
Don't forget to include space for things like shadow copies on Windows systems and backups on disk.
If you have more than one class of storage, you need to make the calculations for each class separately as well. It's not unusual to find that slower data storage classes are growing quickly (often due to regulatory requirements), while the more expensive and fast storage for mission-critical applications is growing relatively slowly. In this case you should be able to save money by adding less, or no, fast storage while increasing the amount of slower, cheaper storage.
Are you planning any major expansions or modifications to your IT system?
The questions addressed up to this point deal only with "natural" growth, or the product of ordinary IT operations in a more-or-less static environment. However, most data storage environments aren't static, meaning storage capacity planning becomes more complex, and more nebulous.
Ask yourself if you are planning any major initiatives that will affect storage needs in the next year. That includes things like system or server upgrades, adding more employees, expanding the business, etc. You'll have to estimate the effect that these kinds of things will have on your data storage needs.
Are there places you can save capacity?
Looking for ways you can save capacity is optional, but it is often a worthwhile use of your time. Simply switching from RAID 10 to RAID 5, for example, can save significant array space. Storage virtualization and thin provisioning can also yield more capacity by letting you utilize under-utilized storage. Plus, data deduplication and archiving older data have the potential to produce major savings in storage capacity.
In the end, asking yourself these questions will better help you map out your data storage capacity plans. Knowing the tools at hand you can use, your immediate storage requirements, your data storage growth rate, your plans for the future and exploring where you can save capacity and reduce data will make the data storage capacity planning process much simpler and less overwhelming.
About the author: Rick Cook specializes in writing about issues related to storage and storage management.