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Old 10-24-2012, 03:32 AM   #1
hydraMax
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SD cards for long term storage?


How do SD cards do as long term storage devices? For example: Say I take some digital photos or videos or something and I put them on, say, a 16GB SD card, and then stick the SD card in a drawer and forget about it. Then I come back a year later. Will I still be able to read the data? What about two years? Five years? Longer...?
 
Old 10-24-2012, 04:33 AM   #2
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If you just google your question you will find a lot of good info. Such as http://www.guardian.co.uk/technology...p-data-storage
 
Old 10-24-2012, 12:10 PM   #3
hydraMax
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Quote:
Originally Posted by bubuntu View Post
If you just google your question you will find a lot of good info. Such as http://www.guardian.co.uk/technology...p-data-storage
According to the link you provided, SD cards shouldn't be used for archival storage because "the charge will decay over a long period", but the author indicated that he is "sure they will last five years, and there's a reasonable chance of (sic) they will last up to 10 years unattended and unrefreshed". On that note: To "refresh" the memory on the card, is it enough to just stick the card in reader? Or do I have to touch every file on the card or something? If it isn't too much bother to refresh, then I could just get into the habit of refreshing all my cards once every year or two.
 
Old 10-25-2012, 05:29 AM   #4
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Good question. I'm certainly no expert i just passed on one of the links I found as a gental suggestion that there is a lot of info on the internet. However it is conflicting as googling the key phrase of your new question "refresh the memory on the card" resulted in this http://www.wisegeek.org/what-is-a-memory-card.htm# which says you don't need to worry. Go figure. Modifying the search to "refresh the memory on the sd card" found this http://panasonic.net/avc/sdcard/prof...formation.html which indicates some cards would refresh just by being plugged in once in a while. To get a reliable answer will take some research. Maybe "how do sd memory cards work". This http://computer.howstuffworks.com/flash-memory.htm is interesting but a little technical and doesn't answer the question. But it does indicate that the charge on each memory cell will decay over time as we suspected, requiring the need to refresh.

The brute force way would be to copy data from one card to another but the you run the risk of damaging the card by writing to it too much.

I'd say nothing you do will make the card last forever so save the data to more than one media such as CD or DVDs. A lot of trouble I know but you just have to decide how important your data is. Maybe someone can give us a good answer. I'll look into it a little more as time allows.

One more interesting link. http://photonaturalist.net/11-tips-f...card-problems/

Last edited by bubuntu; 10-25-2012 at 07:25 AM. Reason: added link
 
Old 10-25-2012, 07:39 AM   #5
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There are three main problems:

1) As said above the change will decay, this means that data will be lost at some unknown point in the future depending on the quality of the card and other things.
2) Recovery of data from a dead flash media card is virtually impossible. I have never seen it done, but there are services that claim they can do it. You take your chances, as they can fail suddenly and completely without ANY warning. There is no SMART, no any type of health indicator, no nothing. It's just not designed for this purpose.
3) Corruption is common and varies greatly with the quality of the card and of the reader. I have noticed this from personal experience. Cheap, low quality readers and cards just corrupt the data. I suppose this is why they say to format the card often. The corruption may also be from charge decay of filesystem structures. (see #1).

Conclusion: If you care about your data, do NOT use flash media for backup, because it just isn't designed for it or a good idea.

I personally use DVDs, and if they are stored properly they will last a long time. People are going to argue with me, claiming that they lost disks soon after burning them. Again it also depends on the quality of the disk, storage conditions, and quality of the burn.
 
Old 10-25-2012, 10:25 AM   #6
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I know a guy who had this problem and the solution he came up with was 2 hard disks, on the basis that both wouldn't fail at the same time.One was usually live somewhere, and one in a drawer.
 
Old 10-25-2012, 11:50 AM   #7
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Quote:
Originally Posted by business_kid View Post
I know a guy who had this problem and the solution he came up with was 2 hard disks, on the basis that both wouldn't fail at the same time.One was usually live somewhere, and one in a drawer.
That is an option, in fact I do use that as well, but there is the rare coincidence in which both will fail at the same time.

Some may also recommend RAID, and although it does work, it is designed for keeping server data up rather than backing up data. What if lightning strikes the box and the surge protector is fried ?
 
Old 10-25-2012, 09:46 PM   #8
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You could also use one of the internet data storage sites. There are lots of them. Nothing lasts forever so using different media and multiple copies I think is the best approach.
 
Old 04-30-2013, 09:29 AM   #9
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Quote:
Originally Posted by H_TeXMeX_H View Post
3) Corruption is common and varies greatly with the quality of the card and of the reader. I have noticed this from personal experience. Cheap, low quality readers and cards just corrupt the data. I suppose this is why they say to format the card often. The corruption may also be from charge decay of filesystem structures. (see #1).
I just wanted to add a bit more info from personal experience. Usb sticks and SD cards seem to leak change in the time span of only a few years. I have followed 3 usb sticks and 10 SD cards for a number of years, storing data on them and working with them. The filesystem eventually becomes corrupt after 3-4 years of use. It must then be refreshed by re-formatting it.

I've recently had a USB stick that I bought a few years back (3-4 years) become corrupt. I thought it was dieing, but after wiping it with random data and re-formatting it, it seems to work just fine. I have loaded it with data and checked md5sums and there is no more corruption. The corruption seems to happen after copying files onto it, usually many files. You can see the corruption of the FAT if using a FAT filesystem and you may get I/O errors or read-only errors. These all disappear after re-formatting.

As the filesystem is the first thing to be written to the USB stick, it is the first thing that will fail because of charge leaking. As this has happened only on flash media and with both SD cards and USB sticks, it must be change leaking.

Someone asked how long it would take for charge to leak, and hopefully this is an attempt at an answer. I'd say the charge would last a max 5 years without re-formatting or re-writing it.

Last edited by H_TeXMeX_H; 04-30-2013 at 09:31 AM.
 
Old 04-30-2013, 09:57 AM   #10
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I think the answer here, as always, is never have just one backup. Always back up onto more than one medium, always test the backups and always assume that any backup medium will only last a year.
For long term storage only an archival medium will work and they're not generally cheap.

Last edited by 273; 04-30-2013 at 09:58 AM.
 
Old 04-30-2013, 03:33 PM   #11
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I have had many professional CF disks for use in high end camera's work very well for years. They did cost me a BUNCH when new so I assume I got what I paid for and not just a warranty.

I'd guess you could expect a professional CF disk to be stable for maybe 5 years if kept safe. I wouldn't expect much more.


A hard drive would be best choice unless you could make a pressed cd. They'd last maybe 20 or 30 years.
 
Old 04-30-2013, 07:05 PM   #12
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Look at something called M-Disc. Yes, need a special drive to burn them, but they are "rock-like" DVDs. Just bought a new BD-RE drive and noticed it handled those as well, Google knows more than I do.

On topic, best luck I've had with SD cards was 2-3 years, then things started getting corrupted, or becoming unmountable.
 
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Old 05-01-2013, 09:36 AM   #13
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LTO tape!

Alternatively, burn DVD and keep in a cool dark place and re-burn to new media every year or two.
 
  


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