I have a large collection of video files most of them in mp4 format. I currently store them in SD Cards. Once I finish filling a SD Card I lock it and never use it again unless I need to read the files.
My intention is to be able to read those files in 30 years. I have been researching and it appears that even If I don’t use the card and properly store it some data degradation will occur. Is that right? I also tried to compare it with other storage Medias but most of the information I have found online don’t come from “official” sources.
There is any way of refreshing the charge in SD cards without copying in and out the information manually or should I replace the cards every five years?
26 Answers
The question is two years old but still relevant. I've had same problem on archiving an huge image archive. Will answer to the question marked in bold.
No, you don't have to replace the SD cards. You only need to refresh them just plugging them in a device capable of read/write them, and use any tool that reads sectors on disk and rewrite them unchanged. This procedure may be done just once every 4 years, that is shorter than the average life span of stored bits. Manifacturer's quality applies.
As Hennes pointed up, still today year 2016, the best media for long term and untouched storage is magnetic tape. But it suffers from being sensitive to magnetic fields and the fast obsolescence of media readers: after 20 years it may be possible you haven't a working tape reader for your data.
De facto, the actual best long term storage are quality SD cards plus the 4 year refresh. This is good for sensitive/military/strategic archives, because every 4 years you can assess the status-quo of technology and if you decide to move the archival media to another thing, you have commercially available both media readers/writers and transfer data to the new medium without the pain of find any reader for the old one.
Another good practice, is have always at disposal two (or more, depends how much important the data is) copies of the archive, stored in different places, so you can recover data being destroyed by other means than media degrade.
I will not support the use of mechanical drives for long term storage because it is proven a sitting HDD may fail to start again if stored more than one year untouched, on the average. It may fail even sooner.
4If I don’t use the card and properly store it some data degradation will occur. Is that right?
Yes. But the same is true for most storage media.
If you want to keep things for a long long time, then copy it every now and then, where the time period depends on the medium used. Old fashioned tapes still rule for this, but for consumer consider the following:
- Copy all to a single pair of harddisks (cheap media compared to SD cards)
(and happily re-use the SD card. Do not bother buying dozens of those). - Every year update one of the harddisks (e.g. wipe the old data, copy all files (including new ones) to it.
- Store this disk somewhere safe (So that a fire will not wipe both backups).
- Next backup write to the alternative disk.
That way both backup devices get used and keep fresh data.
Given human nature and the quick size increases of data (e.g. higher resolution recordings) you might up ending replacing a disk every few years. This is a good thing! It means you keep backup up to something which is not too old and which you can read without using one ancient computer which might break.
(Just think of backups on floppies, or in 5 years of backups on PATA drives).
4A further precaution for long term storage of important data is to generate parity files for the data. I use QuickPar on Windows, but it's pretty old. If you make parity files 5% the size of the data, you can repair up to 5% damage.
You need special, inexpensive, recovery software to read bad files from DVD. I don't know what happens when a file on an SD card becomes corrupt. You may or may not need special software to get a copy including the errors off the card rather than just a "failure to copy" error. With images it wouldn't matter whether you could copy the damaged file off the card since you can reconstruct the whole file. But giant video files would be a problem.
I would recommend using cloud storage like Flickr, Pinterest, or similar sites. Flickr allows 1TB of free storage for photos.
Also understand that the write-protect switch on an SD card works like the write-protect tab on a 3.5" disk. It doesn't actually do anything, and requires the device to honor the switch to prevent writing to the card. it could happily ignore the switch position, and write to the card.
If you use Linux, you could try
dd if=/dev/sdX of=/dev/nullwithout mounting the card, where sdX is your SD card.
This should just read the card itself without copying any actual data (/dev/null is a void device, a black hole of some sort), hence "refreshing" the bits inside the cells.
2Use a Windows PC to perform a disk check. Make sure "scan for and attempt to recover bad sectors" is checked. This will read and write to every data block on the device, thus refreshing it. Plus it has the added benefit of re-mapping blocks that may no longer be usable.
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