All nonvolatile memory cards use a similar mechanism for data storage, regardless of format. While there are choices in the manufacturing process that can result in higher or lower reliability, none of the cards can provide any guarantee against failure or eventual wearout. Careful handling and proper storage can improve your odds, as well.

While these cards are not magnetic storage, the organization of data for storage, and the management of the stored data, is very similar to that on a magnetic (or optical) disk. As a result, failures can occur in several different ways. A "bad" area can develop in the space where file index information is stored. Many times, this renders the entire device unusable immediately. And reformatting will try to build a new index (or File Allocation Table) in the bad area. That format will usually fail and produce some sort of error message indicating that the device is not usable.

Alternatively, the bad area can develop in a part of the device where only data is stored. In this case, files in that area will be corrupted, and sometimes access even to files in the "good" area can be affected. Reformatting can usually fix this by creating a table that tells the system to map around the bad part and not use it. The long form format may be required to accomplish this. The device can continue to be used in this case. In fact, you are probably using memory cards right now on which this has happened, perhaps several times, and you aren't even aware of it. The only impact is a slight reduction in the capacity of the memory card.

Also...if your camera handles "big" memory cards, but not "really big" ones, you might check whether there has been a firmware update which has increased the size of cards recognized. I know that I have several older bodies that can now use cards that go far beyond those that were compatible when the cameras were originally delivered as a result of firmware updates that I have installed over the years.

When you consider the amount of data that we record, the failure rate is actually pretty low in terms of the number of bytes written and read. But it is not zero. The nature of volatile memory design and function is that the cards are born dying a slow death. They are not intended as archival storage devices and they do not necessarily provide warning of impending failure.

Oh...a couple of last things. Always format memory cards in the device that is going to be writing to them. You may want to occasionally do a long format and diagnostics on your computer, which is good (if done only occasionally). But if you do, reformat in the camera before using them again. And remember that formatting involves writing, so don't go overboard with this. I also suggest that if you use large capacity cards, download often by copying to your new destination, but don't continually delete or move files from partially filled cards. Doing so puts an excessive number of "write cycles" on the lower memory locations, and increasing numbers of cycles is what leads to wearout. So distribute wear across cards by leaving pictures in the lower locations until the card is nearly full. And if you never fill a card beyond half (or one quarter) full, you would be better served by buying smaller cards.

Point well taken. I'm sorry about your camera being stolen. Several years ago, I was visiting an aquatic park in Hawaii. I was resting on a bench and there was an Asian family sitting on a bench across from me - about 30 feet away. I noticed that the gentleman of the group had a new Nikon DSLR. I looked away for some period of time and when I looked back, the family was gone but he had left the camera on the bench. I rushed over to pick it up hoping that he hadn't gotten too far away so that I could return it to him. They were nowhere in sight so I took it to the ticket sales booth and told them what happened. I spent several more hours at the aquatic park and I was constantly on the lookout for this family hoping to tell them that I had found their camera and they could pick it up at the ticket booth. I never saw them again and I have often wondered if they ever recovered their camera.

All nonvolatile memory cards use a similar mechanism for data storage, regardless of format. While there are choices in the manufacturing process that can result in higher or lower reliability, none of the cards can provide any guarantee against failure or eventual wearout. Careful handling and proper storage can improve your odds, as well.

While these cards are not magnetic storage, the organization of data for storage, and the management of the stored data, is very similar to that on a magnetic (or optical) disk. As a result, failures can occur in several different ways. A "bad" area can develop in the space where file index information is stored. Many times, this renders the entire device unusable immediately. And reformatting will try to build a new index (or File Allocation Table) in the bad area. That format will usually fail and produce some sort of error message indicating that the device is not usable.

Alternatively, the bad area can develop in a part of the device where only data is stored. In this case, files in that area will be corrupted, and sometimes access even to files in the "good" area can be affected. Reformatting can usually fix this by creating a table that tells the system to map around the bad part and not use it. The long form format may be required to accomplish this. The device can continue to be used in this case. In fact, you are probably using memory cards right now on which this has happened, perhaps several times, and you aren't even aware of it. The only impact is a slight reduction in the capacity of the memory card.

Also...if your camera handles "big" memory cards, but not "really big" ones, you might check whether there has been a firmware update which has increased the size of cards recognized. I know that I have several older bodies that can now use cards that go far beyond those that were compatible when the cameras were originally delivered as a result of firmware updates that I have installed over the years.

When you consider the amount of data that we record, the failure rate is actually pretty low in terms of the number of bytes written and read. But it is not zero. The nature of non-volatile memory design and function is that the cards are born dying a slow death. They are not intended as archival storage devices and they do not necessarily provide warning of impending failure.

Oh...a couple of last things. Always format memory cards in the device that is going to be writing to them. You may want to occasionally do a long format and diagnostics on your computer, which is good (if done only occasionally). But if you do, reformat in the camera before using them again. And remember that formatting involves writing, so don't go overboard with this. I also suggest that if you use large capacity cards, download often by copying to your new destination, but don't continually delete or move files from partially filled cards. Doing so puts an excessive number of "write cycles" on the lower memory locations, and increasing numbers of cycles is what leads to wearout. So distribute wear across cards by leaving pictures in the lower locations until the card is nearly full. And if you never fill a card beyond half (or one quarter) full, you would be better served by buying smaller cards.

I've been using SD memory cards since they first came out and for more than just photography. Frankly, I had heard of failures, but considered these cards to be nearly bullet proof since I had never had a problem. That all changed last weekend after coming home from a local event and finding out that I could not read or write from one of the two cards in my Pentax K3. Thankfully, the K3 has the dual card system and the other card was fine, but I had no idea that there was any sort of problem while shooting and there were several shots that I considered to be rather important from this shoot.

Anyway, my reason for posting this is to point out how important that second slot can be as a backup, as I would have been really upset if I had lost the photos from this shoot. It really makes me wonder why any manufacturer would bring out a new camera body or system without a dual slot available. I personally will never own another one without the backup slot, lesson learned! By the way, the defective SD card appears to format normally, but will not otherwise read or write in either my camera or on my computer system and I have no idea what might have caused this failure. Good luck and good shooting to all.

Not necessarily. I am just suggesting that for longest life, don't be continually writing to a small area on a mostly empty card. The life of the 'bits' is based on the number of times they are written to. Rotating cards is fine. I'd just not delete files (or Move them) each time if the card is not very full, because you are always going to be writin to the same place. If you are filling the card up each time, you are already getting maximumm use out of it.

Not sure this is very clear. Does it help?