By Mike Talon
When creating disaster recovery plans, we often deal with strict "black and white" factors. In other words, we nearly always look at data in terms of whether we need to protect it and develop policies based specifically on that decision.
However, particularly in the case of end-user file servers and network-attached storage (NAS) devices, many files and data sets fall into the "gray area"—data that isn't important enough to include in the DR plan, which corporate policies still allow to exist.
The most common examples are temporary files created by software and suites, such as Microsoft Office and WordPerfect, temporary and/or testing databases or code for the development staff, and personal files that corporate policies allow users to store on corporate data systems. While most of these files aren't vital for corporate operations, either end users or software uses them, and they therefore require space on corporate data systems.
When developing a DR plan, your first priority is to create a system that can protect the vital data and make sure it's available if a disaster destroys the original systems or otherwise incapacitates them. In this process, you must make some important decisions about these gray-area files to ensure you don't leave out something vital.
You must first decide whether to replicate or back up gray-area files. Doing so is the easiest way to make sure you protect all the vital files, but it also means you're going to either transmit and/or back up a great deal of nonvital data in many cases.
This requires extra tape resources, extra disk space, and potentially greater bandwidth costs. It could also mean higher software and hardware costs as you move toward "enterprise" or "advanced" editions of backup and/or replication tools.
Choosing not to replicate or back up these systems often requires less hardware and software to perform the DR operations, but you could incur additional management overhead when implementing and maintaining the systems themselves. You need to perform a comprehensive study to determine what is and what isn't a gray-area file in your organization.
Once you make this distinction, you must determine the best way to exclude those files. This isn't as easy as you might think.
If you use backup tools, you can selectively exclude many files by their extensions or other file patterns. However, many files can be indistinguishable from vital files.
In these cases, you must find a way to segregate these files—presumably by file directories—so you can ensure the system protects only vital files. If you use a replication system, you may also run into additional issues.
Software-based replication tools often allow the same level of file recognition as tape systems, so you can use the same techniques to protect only vital data. Hardware-based replication systems generally can't distinguish one file from another, so you'll need to segregate files into directories or even data volumes.
Regardless of whether you decide to protect gray-area files, they exist in every organization. However, in most companies, the IT staff doesn't make the decision of what users can store on data systems, especially file servers and NAS devices.
Corporate standards, executive privileges, and other factors will always create gray-area files. How you choose to handle these files can make the difference between a successful and an unsuccessful DR plan when it's time to fail over.
Mike Talon is an IT consultant and freelance journalist who has worked for both traditional businesses and dot-com startups.