Guest
[Entry]
"Durability
In my experience, memory cards are quite durable, though occasionally finicky when it comes to formats. I recently ran a cellphone through the washing machine (it was so dirty), and the 2 GB microSD card works just fine in my new phone (I eventually got the washed phone working too, but it was a good excuse to upgrade).
Rob Galbraith, who maintains an amazing website on CompactFlash and Secure Digital cards, says
Individual flash memory cells have a limited lifespan. That's the bad news. The good news is that their lifespan is usually measured in the many, many thousands of erase/write cycles, and that card controllers use an algorithm that balances the wear across the entire card's cells. CompactFlash and SD/SDHC cards are designed to automatically and transparently map out memory cells that go bad, or in some cases when they reach a predefined limit.
Write cycles are important, but MTBF (mean time between failures) is often 1M-2M hours or more, factoring in advances such as wear leveling, bad-block marking and management, etc.
Tips
Do not defrag a memory card. This consumes write/erase cycles and shortens the MTBF.
Use FAT32 instead of a journaling file system (like NTFS), which will write more often.
SD cards are rated to hold data at something like 10 years sitting idle. I recall reading (not sure where) about re-energizing cards by occasionally inserting into a reader.
Anecdotes
The 2004 BBC article Digital memories survive extremes covers an interesting study by Digital Camera Shopper on the durability of memory cards.
The memory cards in most cameras are virtually indestructible, found Digital Camera Shopper magazine. Five memory card formats survived being boiled, trampled, washed and dunked in coffee or cola.
In 2004, there was an incident (covered happily in a SanDisk press release at the time) where a photographer's compact flash card survived a bridge explosion where the camera gear was set up so close to the blast that it was destroyed, but the CompactFlash card survived. Other incidents like plane crashes are hyped by SanDisk so much that, admittedly, I get nervous using other brands. That said, it's not always easy to get data from a damaged card. An atmospheric research balloon crashed in the Pacific Ocean and was recovered. One SD card was read easily but another required intervention from SanDisk, but it was eventually read.
Bill Biggart's photos from 9/11 survived the collapse of the second tower on a CompactFlash microdrive card.
Recovery
If you suspect a card may be getting flakey, or if you run into trouble reading a card, immediately create a backup of everything on the card. There are low-level recovery tools like TestDisk and PhotoRec that come in handy for this."
|
