Solid State Drives and Flash Memory

Discussion in 'General Electronics Chat' started by iONic, Jan 5, 2012.

  1. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    For those who understand the workings of Solid State Drives and Flash Memory.
    ...that doesn't include me!!

    There IS a lifetime issue with data stored on a flash drive. Data is stored as a series of static charges - over time those charges will dissipate and your data will evaporate. Some papers suggest that something like 10 years is a reasonable expectation for data to be retained before this starts to become an issue.

    Is this the same for SSD's? They are nothing more than piggybacked Flash memory, yes?

    If so, then would just plugging in the flash drive or turning on the SSD "re-charge" the stored data?

    Apparently strong electromagnetic fields still disturb both HDD's and SSD's.
     
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    10 years ago was 2002. I don't think I have *any* drives from that long ago.

    I do have some floppies from my old TRS-80, though. Wonder if they still work?

    Edit: *Flashback*!!! My original post said 10 y.a. was 1992. Boy, I'm out of it today!
     
  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Not unless you read and overwrite the whole disk. Just powering up the disk will do nothing to the charges stored in the flash cells.

    For offline storage, I would still use multiple copies on standard harddisks. But if you wanted your data to last very long, periodically copying them to new fresh disks might not be a bad idea, because you never know what long term effects might do to various materials used inside.
     
  4. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    Then perhaps CD's/DVD's are better?...unless you live in Arizona leave your disks on the window sill.

    Or: Perhaps a HDD with 2 partitions, both of which can hold the backed up content and rewritten over periodically from partition to partition. I know I have data that have time stamps as old as 1987. They are not on the original media and have probably been moved more than once......hopefully!
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I wouldn´t trust DVDs or CDs, some I had didnt last even 4 years..

    Partitions sadly won´t protect you from the death of the disc´s mechanical parts like the fluid bearings of the platter motor, you never know what will the lubricant do in ten years. AFAIK magnetic tapes are still the most reliable long term storage, apart from carving your data into stone ;)

    But the cheapest way would be buying two different disks from different manufacturers and periodically checking if they are still allright.
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Periodically refreshing the SSD could work too. But having two physical media preferably in different locations is allways better.

    You need to decide how much you value your data and how much you are willing to spend (for example each year) to be sure you still have it. From that you can decide how elaborate the backup can be. Two new HDDs every two years will cost you about 100$ a year which seems a reasonable price to store your memories and important stuff, at least to me. (when the disk prices get to their normal levels)

    Anyway, it is nice talking about how it should be done, when anytime I buy a new disk I just fill it up almost instantly instead of finally backing up the important stuff and storing it in a safe... :D
     
  7. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    I have a old raid 5 scsi backup system (separated from the house (in the man cave) with a 1 Gb Ethernet link) with some enterprise rated 5 1/4 inch 20G drives with a hot spare that archives my most valuable digital data. I also use rsysc to copy versions of the data to all my Linux systems when they are running. I would not trust SSD drives with something that can't be replaced. You can usually recover data from a platter unless there was a total head crash but data forensics on dead flash drive because of internal chip failures is tricky.

    Use archive quality CD and DVD media. A archive quality CD lifetime is estimated to be 300 years and 70+ years for an archive quality DVD.
    http://www.yuden.co.jp/ut/product/category/media/
     
  8. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    I am a bit skeptical of your choice of CD/DVD media. I've never heard of the company. I generally go towards Verbatim for decent quality. This would be a good mission, to research the archival quality of CD/DVD/BluRay. And to add to that, a quality comparison of the recording equipment as well.

    I bought a 80GB HDD for my mother to backup all her data(pictures essentially).
    Once a year I turn on the drive and copy another years worth of images to the drive, then unplug the drive. I guess I have about 5 years before I have to copy the data to another drive or rewrite it on the same drive before it starts to
    fade away!
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    The price of terabyte drives has gone down enough to do a mirror of your system once a month. Date drive, store in a freezer.

    Preferably store backups in separate locations, in a cool to cold environment (unless it is tape). For tape, store at 60 degrees.
     
  10. tom66

    Senior Member

    May 9, 2009
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    The -data retention- of a good flash memory chip is of the order of 50-100 years at room temperature. It falls with higher temperatures, but you still get at least 15-20 years at 85°C (typically.)

    The problem with flash memory endurance is writing. A cell is normally "1" - that is the erased value. When data is written, charge is put on the floating gate through quantum tunnelling, making the data a 0. Here's the problem: If you keep doing this quantum tunnelling stuff, you wear out the gate, so it can no longer accept new changes but it still retains the original data. So it will become slower and slower to write data and eventually data will no longer be able to be written to that cell.
     
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