The role of tape is clearly changing, shifting away from everyday data backup and moving toward deep archiving or offsite storage, but tape is still an important element of many data centers. Storage professionals must contend with concerns about tape performance and reliability that have remained almost unchanged for decades. In spite of the many different protective cassette designs introduced over the years, tapes are notoriously sensitive to rough handling and adverse environmental conditions. Tape drives can cause heavy wear on the media even under ideal conditions, and suboptimal communication between the drives and servers can potentially ruin the media. Below are a series of best practices that can help you to get the most service from your tape drive and media investments.
Pay close attention to media storage conditions
Plastic outer cartridges provide a modicum of protection against casual handling, but severe impacts, temperature or humidity extremes, and even airborne particles like dust on exposed tape can lead to premature media damage and data loss. If you store tapes at offsite locations, inspect those facilities periodically to verify proper storage conditions.
Rotate and replace tape media regularly
Tape actually contacts read/write heads, so the media's working life is limited to a certain number of hours or passes running in the drive. Spread out this normal wear by rotating tapes within your working media set. Keep track
Maintain the tape drive properly
The movement of tape media in the drive will eventually deposit media onto the drive's read/write heads, and this can easily result in media errors or even cause premature damage to the media. Be sure to follow any maintenance recommendations from the drive manufacturer such as head cleaning. If your tape system or library has a service contract, the service vendor should provide routine cleaning and maintenance. Be sure that any service contract renewals cover routine drive maintenance as one of the terms.
Refresh old tape media or convert to another media type
The data stored on magnetic media will slowly decay over time -- even just sitting on a shelf. Eventually, the media will experience data errors, which may make restorations impossible. Make it a point to refresh tape data periodically. This isn't a problem when a tape is in normal rotation, but tapes relegated to deep archival storage can become problematic over time. Implement a refresh program that will allow you to refresh (rewrite) tapes that approach 50% of their long-term storage life.
It may also be necessary to refresh old archival tapes when the tape hardware/software infrastructure changes significantly. For example, moving to a new backup/archive software product or deploying a new tape drive or library platform may render any existing tapes unreadable. In this case, transfer the old tape data to the new tape media. This way you are not obligated to retain the old tape hardware along with the archived media. Some users leery of long-term tape retention may opt away from tape, rewriting onto alternative media such as Blue-Ray (high-capacity) DVD or emerging holographic discs.
Match the backup server to the tape drive
Tape drive and server performance is often mismatched, and the server cannot pass data to the drive fast enough. The tape drive must then stop, rewind the tape to new start point and then continue; this process is called shoeshining, and it causes excessive drive and media wear. In many cases, storage organizations will need to upgrade their backup servers in order to keep pace with today's faster drives. Experts note that some organizations can ease shoeshining by processing the backup job to disk first, and then streaming the completed job to the tape system. This approach allows all of the server's processing power to focus on moving backup data rather than creating the backup and moving data at the same time.
Use data reduction technologies to shrink the backup task
Data reduction techniques like data deduplication, conventional compression and delta differencing to reduce the amount of data that must be backed up. Smaller backups will execute faster, resulting in a shorter backup window, less drive wear, and lower media usage (and lower media costs). Most backup software packages today include some combination of data reduction features, though dedicated deduplication appliances are also available.
Upgrade older drives for more speed and capacity
Some organizations can realize improved tape efficiency and media cost reductions by upgrading tape drives to the newest standards. For example, LTO-4 tape drives offer twice the capacity and speed provided by their previous LTO-3 standard. This will help to execute backup tasks faster while using less media. A move to more efficient tape is often combined with data reduction technologies for even more benefit.
Be sure to consider compatibility when making an upgrade. For example, an existing DDO tape cartridge will not be readable in a new LTO-4 tape drive. A notable exception here is LTO-3 tapes, which are still readable in LTO-4 tape drives.
Use data backup tools to locate bottlenecks
Experts point to a growing number of backup and data protection management tools that can analyze backup traffic and highlight potential problem areas. For example, you might identify tape as your data bottleneck and spend significant capital dollars for upgrades and other changes -- only to discover that the problem was actually in software configuration. Analytical tools can help to identify trouble spots more quickly and accurately than empirical examination. Common tool vendors include Aptare Inc., Bocada Inc., EMC Corp., Imation Corp., Symantec Corp, Tek-Tools Inc. and WysDM Software Inc.
This was first published in February 2008