Backing Up the Back Up by Steve Cunningham

7/13/2010 12:26:20 PM
By PSN Staff

There's nothing like a hard drive failure to bring one's backup strategy into sharp focus, and lately I seem to be surrounded by hard drive failures. The first incident occurred just before finals week, when I lost my laptop's year-old 500 GB internal drive after a spontaneous crash. The computer simply would not boot up again, although I could hear it spinning. A couple weeks later, a similar failure struck the five-year old drive in a desktop computer at home. Shortly after that I got a call from a colleague inquiring whether I could help him with an identical pair of external drives that he'd owned for two years, and which his computer no longer recognized. It turned out that each of the hard drives involved had suffered mechanical failure, and no amount of software diagnostics, recovery tools, or voodoo rituals could bring them back to life.

I had current weekly backups for both of my drives, although I discovered that just before final exams weekly backups are just not enough. I wish I could say the same for my colleague's drives, but I cannot. His identical drives were alternated to produce rotating backups, and he lost substantial data from the older backups.

Those of us who buy hard disk storage for ourselves or our organization are aware that hard drives have simultaneously increased in capacity and decreased in price. It's actually becoming difficult to buy a hard drive of less that 400 GB capacity. Most are 750 GB and up, which means that losing an entire drive can mean losing a lot more content. Seagate, for example, has announced their upcoming 3 TB drives that could be available before the end of the year. It also means that the 2 TB drives will be significantly marked down. Today I saw a dealer's ad for a Seagate 1.5 terabyte drive for the princely sum of $70 with free shipping. But just how reliable can a huge drive be when it retails for $70 including shipping?


Although drive capacity has increased and manufacturing costs have dropped over time, I wonder whether drive reliability has actually decreased from what it was a decade ago. A Carnegie Mellon University report in 2007 debunked the concept that MTBF (Mean Time Before Failure) was an accurate predictor of hard drive longevity, and indicated that drive failure may begin much earlier than previously thought. Moreover, reliance on on a drive's self-testing SMART function may not give adequate warning, as Google pointed out in it's 2007 report . They found that drives often needed replacement for issues which SMART drive status polling did not or could not determine, and over half of failed drives did not raise any significant SMART flags at all.

Three to five years is considered by professionals to be the useful service life of a consumer-grade hard drive. Yet it may be telling that several drive vendors have reduced the length of their warranty period; Seagate's used to be a full five years on even their consumer drives, but it is now three years for the newest models. Manufacturing missteps which caused drives to fail prematurely have added to customer concerns over decreasing service life. Simply checking out customer ratings for hard drives on vendors' websites reveals a decline in quality and an increase in infant mortality -- hard drives that die within 30 days of use -- along with more negative comments and ratings from those who bought troubled drives.


If what I believe I am seeing is correct, then data backup is more essential than ever given the size of today's hard drives. I'm a fan of the 3-2-1 rule, a strategy developed by digital photographer Peter Krogh in his book "The DAM Book: Digital Asset Management for Photographers". This rule states that one should have three copies of any file (that's three different devices, not three copies on the same device), two different media types (like hard drive and recordable DVD, for instance), and one of the copies should be stored off-site. The off-campus requirement can be met with an external drive that leaves the office, or an Internet-based backup system such as Carbonite or Mozy . These services do the job, although in my experience the first backup can be extremely slow and frustrating. Additionally, these services will only backup internal computer drives and not external drives, even if those external drives are connected and mounted.

The ultimate answer to this entire issue may be to buy large drives in pairs, then create a personal backup system with them in a RAID 1 configuration. This solution provides the peace of mind that comes with redundancy, as RAID 1 constantly writes identical data to each of the two drives. RAID 1 enclosures that hold two or four drives are readily available and reasonably priced, and may represent the only safe way to deploy large hard drives that are impossibly inexpensive.

Meanwhile, please excuse me—I need to go backup my backup.

Steven Cunningham is an assistant professor of practice at USC's Thorton School of Music.

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