I recently came across product information for a "new" type of digital storage device from SanDisk. The Memory Vault with Chronolock technology is designed for permanent storage of important photographic memories.
The SanDisk marketing materials promise 100 year life and provide very technical explanations of how this number is arrived at with the prominent placement of the Arrhenius equation on the page devoted to the technology behind the Memory Vault and SanDisk's
memory retention testing methodology
. This sort of accelerated life testing is well-known in microelectronics. An activation energy is applied in the Arrhenius equation to determine how long a useful life a piece of equipment will enjoy at typical operating temperatures based on a shortened lifetime produced during testing at much higher temperature. SanDisk testing claims that their Memory Vault will enjoy "at least 100 years of data retention."
As the SanDisk product pages describe it, "The Memory Vault memory system contains a combination of a proprietary ASIC controller, non-volatile memory, and a system firmware to tie the two together." But will a special ASIC memory controller interfacing standard NAND flash memory that simply locks down write access with firmware be all that's inside? I wouldn't be too sure that it really is (or that your photos would be perfectly safe if it is).
You see, there once was a type of non-volatile solid-state memory in development that was perfectly suited to archival data storage. A one-time programmable (OTP) type of truly permanent memory based upon an anti-fuse cell was developed by Matrix Semiconductor. They called their technology Matrix 3D Memory . Oddly enough, SanDisk acquired them in 2005, a fact which is obviously driving my rampant (and recurring) speculation.
To me, the Matrix approach is the obvious solution to ensuring digital bits are not disappearing over time, fading the digital images they are storing as time goes by. The Matrix cell technology was scalable and offered an inexpensive and extremely robust archival solid-state storage mechanism.
Once again (if you haven't followed earlier rants on this topic ) here is the rationale. Serious photographers know all too well the pitfalls of digital memory systems. The now ubiquitous NAND flash memories are extremely versatile. They are dense, packing many gigabytes into postage stamp sized SD cards. They are re-usable and can be re-written over the course of many years. They are known as non-volatile, but this expression is apt only over the short term. Flash memories in common use for camera cards are virtually all based on floating gate memory technology. Digital bits are stored in the form of electrical charge placed on an isolated capacitor plate - the floating gate. The terminology arises from the fact that the so-called floating gate is electrically isolated or disconnected from the rest of the circuit. Writing a cell by storing charge is accomplished through some nifty semiconductor physics with careful adjustment of the various terminal voltages applied to the cell to allow the electrons to overcome (or tunnel) through the potential barrier of the insulators to arrive at the storage site on the floating gate. This stored charge on a floating gate influences the operation of the transistor element that makes up the cell to allow the read out circuits to detect the presence of a "1" or "0" on the cell.
Unfortunately for those looking to keep precious photo memories around for a long time, erasing can be accomplished in very similar fashion (with apologies to readers who are well-versed in non-volatile memory technology). Worse, the processes that influence charge transfer in the flash memory (and elsewhere of course) depend on a number of environmental factors - chiefly temperature. The upshot is that the baby photos of your daughter or grandson are left lying around in hot places long enough, you are bound to get some data corruption and possibly even lose files altogether.
Now of course, conventional floating gate flash memory is extremely well characterized since it has been the workhorse non-volatile solid-state memory for decades now. As such, manufacturers have hit upon a few minimum goals for the technology based on specifications such as the number of re-write cycles and data retention - the main point of this discussion.
Without getting deep into the details, many of these specifications are statistical and based on ranges of environmental operating conditions. What this all boils down to is that your important data has a very good chance of surviving but with a relatively small (but still significant) probability of perishing. Ultimately, it's up to you how much risk you want to take.