Caring For Your Data

"But it booted yesterday!" Sadly this is how some computer users find out why computer professionals like ITS strongly encourage a procedure for regular data backups. Fortunately there are ways to do a little preventive maintenance to keep systems running and your data flowing smoothly.

Hard Drive Life Expectancy

The life expectancy of a hard drive used to be measured in MTBF (mean time before failure), which today is around 500,000 power-on hours. While this may sound like a lot (it is after all 57 years), keep in mind the warranty on most hard drives is one year from the date of manufacture (most drives ITS sells nowadays have a three year manufacturer's warranty). In addition MTBF is the mean (average) time, not the minimum time, between failures. Weighing in on the equation are other factors such as the number of start/stop cycles, heat, usage patterns, and the like.

As a result many manufacturers now use other methods of predicting drive reliability, such as Component Design Life (CDL) and Annualized Failure Rate (AFR). The Component Design Life of current Western Digital drive models, for example, is 5 years and the Annualized Failure Rate is less than 0.8%.

What that means is that users should consider replacing either their computer, or at least its hard drive, every four to five years at a minimum. If your computer is older than that, it would not be unexpected if its hard drive experiences a data error. Fortunately new, larger, and faster hard drives are available for less than $100, and with today's utilities it takes only minutes to copy from the old drive to the new drive. In this case a little prevention can avoid the risk of lost data and unexpected downtime.

Backup Systems

A similar situation exists with backup tapes. Here, magnetic tapes will eventually wear out as the tape slides across the drive's read and write heads. Over time the magnetic particles will essentially be worn off. A cleaning tape can be used to clean the residue off the drive heads, but it becomes necessary to replace tapes as they lose magnetism. ITS normally sets clients up using a weekly backup schedule where full backups are made on Fridays and differential backups made other days. In this situation the daily tapes should probably be replaced every one to two years, the Friday tapes every four years or so.

Recordable CDs are in the same boat, since they will eventually experience degradation as well. If CD-Rs are stored correctly they can last a long time. CD-RWs that were rewritten frequently reportedly suffer a reduced shelf life.

Complicating this is the drive model turnover from vendors. Businesses that prefer to archive old data to tape or CD must retain a method to read that data five or ten years down the road! Otherwise, the old tape drive must either be maintained or the data transferred to a newer tape technology to allow future access to the data. Transferring old data to new media also ensures the media does not fail over time.

For this reason ITS suggests maintaining old data on the network server's hard drive, where it can be easily backed up to multiple sources, and copied to a new hard drive whenever the server is upgraded. Periodic backups can be stored offsite.

April 2004

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