Back in February I wrote about the reliability of flash drives. Because of their ever increasing capacity for storage, coupled with their convenient size, they have become the storage media of choice. But I still have the same questions as to how reliable are they? Are flash drives suitable for long term or archival storage? How do they stack up to other storage devices. Have there been any recent changes in the reliability? Recently, in a discussion at the Mesa Regional Family History Center, two of my colleagues were discussing flash drives. I happened to mention the issue of read/write failure due to repeated usage since there is limit to the number of times you can write to a flash cell. One of the workers, said he had been in semiconductors his whole life and had never heard of such an issue. He simply did not believe me.
I recall the discussion surrounding the introduction and use of CDs and DVDs. They were originally claimed to have a storage life of more than ten years (or even longer). Adequate archive management cannot rely on the claims of manufacturers and anyone interested in long term storage needs to be assured that the storage figures are provable. In the case of CDs and DVDs the storage life turned out to be highly overrated. Here is an article on CD-R/DVD-R reliability.
Flash drives instinctively appear to be almost perfect storage devices. They are portable, easy to use and work with almost all computers. But what is the downside? First of all their very portability makes them a rather unreliable storage media. They are very easily lost. At the Center we have a drawer dedicated to lost flash drives. Regularly, visitors to the Center forget their drives and leave them plugged into a computer. Unfortunately, those same people seldom have their name or contact information anywhere on the drive. It does not matter how reliable the storage device is physically, if it is lost.
Despite my friend's skepticism, flash drives really do have a limit to the number of times you can write to a flash cell sometimes called "write endurance." Manufacturers claims range from 100,000 writes per cell to over a million. These numbers may seem extraordinarily large, but if a flash drive is used for repeated changes to the same document (i.e. genealogy file) it can fail, just like the old floppy disks of years past. The real issue is something called the "hard error rate." The hard error rate can be reduced by software that spreads the read/write cycles over the entire flash drive rather than repeatedly using the same cells.
The engineering types seem to think that the longevity issue has been resolved and that flash drives will last over 50 years even with constant use. Right now, flash drives are not really in the running to replace hard drives. For casual users, they are a reliable solution, but right now the largest flash drives available are 256 GBs, which for my storage demands is way too small. They are also more expensive than hard drives for the same amount of storage. So as of the beginning of 2011, flash drives are a viable portable storage option, but as with every backup situation, use more than one type of storage in more than one location and certainly, don't put all your files on one flash drive.