By Mike Talon
One of my clients had nearly 300 servers spread across the United States, including application servers that ran apps that couldn't be backed up while they were running and file servers with constantly locked-open files. The backup strategy was an absolute nightmare. No matter what time he tried to back up the series of servers, at least one file would get skipped and foul up the entire backup job.
Regardless of what software you use to perform the backup procedure, if anything is holding a file open and/or locked, the backup system will have trouble committing the file to tape. Therefore, you must arrange for the backup to take place while no files are in use or locked—otherwise known as the backup window.
Nearly every disaster recovery engineer who works in the modern digital world—from the largest data center to the smallest single-server setup—has had to deal with the bane of backup windows. As we move more and more toward 24/7 computing, backup windows are shrinking faster than ever. So, how do you deal with backup windows without abandoning the backup?
Most major backup software tools have options for purchase that allow you to back up different applications while they're still running. In addition, there are agents that let you back up locked files on selected operating systems, such as Windows. Examples of Windows files include Microsoft Word and Excel documents.
By using agents, you can successfully back up many—but not all—systems. However, the drawbacks are that agents can cause a large overhead on CPU utilization and other system resources when they're in use. It's also important to keep in mind that not all applications have agents available, and with certain configurations the agents simply don't work.
Another option is to back up the data from a non-production copy. The most common method for doing this is to employ a replication and/or mirroring tool to transmit the data from the production servers to a backup server or other storage device. Tape systems are attached to this device and the backup is made from the secondary storage system.
Most replication tools on the market allow you to copy open files without causing major resource utilization on the production boxes. In addition, these tools are usually built to work alongside backup tools so that you can back up a replicated data set.
The drawback to replication tools is the additional cost of hardware and software. However, this cost is usually justified by the data security you get in return. Another issue is that you can't use the system recovery tools that are available from the backup software manufacturers, because you won't need to back up the production servers.
Nearly every disaster recovery engineer who works in the modern digital world—from the largest data center to the smallest single-server setup—has had to deal with the bane of backup windows. With the proper mix of software and engineering ingenuity, you can create a backup system that eliminates the need for these windows and properly backs up your valuable data.
Mike Talon is an IT consultant and freelance journalist who has worked for both traditional businesses and dot-com startups.