What you will learn in this tip: the differences between autoloaders and tape libraries. Learn about some of the pertinent pricing and compatibility issues when transitioning from an autoloader
With voice and video data becoming more common in the enterprise, some data storage and backup administrators are finding that the volume of data that is being backed up on a nightly basis is growing exponentially. If you find yourself in this situation, then you may eventually discover that the tape autoloader that you're currently using for data backups is no longer sufficient. One possible solution to this dilemma is to invest in a backup tape library.
Backup tape libraries vs. tape autoloaders
Being that both tape libraries and autoloaders can be used to automate backups requiring multiple tapes, it is easy to confuse the two technologies. Autoloaders are typically used in smaller businesses. They consist of a tape drive, a tape magazine and a robotic mechanism that can move tapes between the tape drive and the magazine on an as needed basis.
The biggest difference between an autoloader and a tape library is that tape libraries include two or more tape drives. What are the benefits of having a tape library, as opposed to simply purchasing multiple autoloaders?
The thing that really sets tape libraries apart from autoloaders is that the robotic loading mechanism is able to access all of the tape drives within the library. This allows backup jobs to be run in parallel (which is also possible with multiple autoloaders), but it also helps to improve the reliability of the backup operation. If for example, a tape drive were to fail then the tape library could conceivably continue any backup or restoration operations by using an alternate drive within the tape library.
In addition to normal backup and restore operations, tape libraries are also commonly used for hierarchical storage management (HSM). The basic idea behind hierarchical storage management is that on just about any network, there are files that are almost never accessed. These files consume space on network volumes, and have traditionally been included in regular backups even though the contents of the files rarely if ever change.
Typically, tapes offer a lower price per gigabyte than server hard drives do. Obviously, every tape library is different, but larger tape libraries can include hundreds or even thousands of tapes. Hierarchical storage management remove seldom used files from network volumes and archives the files to tapes within the tape library. These files still appear to reside on network volumes, and remain accessible to users. If a user should ever require access to one of the archived files, the tape library will retrieve the tape containing the requested file, and load it into a tape drive. The file is then moved back to the network volume where it originally resided, and made available to the user.
While this process probably sounds slow, it is important to remember that the tape library knows exactly which tape the requested file resides on. Tape libraries use barcodes to identify individual tapes so that the robotic loading mechanism is able to verify that it is retrieving the correct tape.
Tape library compatibility
If you are seriously considering investing in a tape library, then you probably have quite a few questions regarding how well the tape library will work with your existing backup infrastructure.
The first bit of advice that I would give you is that you shouldn't plan on using your existing tape drives in your new tape libraries. I once did a consulting job for an organization that had recently spent a lot of money on tape drives. They wanted to upgrade to a tape library, but wanted to reuse their existing hardware. Unfortunately though, a phone call to the manufacturer revealed that even though the model of tape drive that the organization was using was also used in tape libraries, it was impossible to retrofit a tape library with an existing tape drive because the drives that the manufacturer provided for tape libraries were using different firmware from what the standalone drives used.
Another compatibility issue is whether or not your current data backup software will work with the tape library that you are considering purchasing. All of the major enterprise backup software vendors offer tape library support in their wares. The catch is that not every backup application works with every tape library. As such, it is important to verify that your backup application is compatible with your intended tape library before making the purchase.
The prices of tape library hardware are widely varied. Refurbished, entry-level tape libraries can cost about $6,000. When sold brand-new, the unit costs just under $10,000. Tape libraries suitable for large organizations can cost anywhere from a quarter of a million dollars on up to well over a million.
Overall, tape libraries offer capabilities that you cannot get with a run-of-the-mill autoloader. Even so, tape libraries tend to be more expensive than autoloaders, and backup scheduling can become more complex due to the existence of multiple tape drives.
About the author: Brien M. Posey, MCSE, has previously received Microsoft's MVP award for Exchange Server, Windows Server and Internet Information Server (IIS). Brien has served as CIO for a nationwide chain of hospitals and was once responsible for the Department of Information Management at Fort Knox. You can visit Brien's personal website at www.brienposey.com.
This was first published in April 2010