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SSD vs HDD Memory storage?

  1. Dec 28, 2014 #1
    1. Which memory storage is better if I want the memory to be durable? Like when I drop it or hit it and still have the least chance of corrupting its memory.
    2. Which memory is better if I want to store it for centuries without rewriting the memory and then be able to access the memory without it going corrupt?
     
  2. jcsd
  3. Dec 29, 2014 #2

    jedishrfu

    Staff: Mentor

  4. Dec 29, 2014 #3
    1. The SSD is better, it doesn't have moving parts so the rapid acceleration/deceleration associated with hitting the ground shouldn't damage the data.
      Keep in mind that I'm assuming the SSD is dropped from a reasonable height, say a desk to the ground. If it's hit by a bat at the end of a 2 storey fall, your data is screwed lol.
      SSDs are more durable, but within reason.
    2. Neither.
      The data will degrade over time if power is not supplied to verify checksums and ensure the integrity of the data.
      Remember, the 1's and 0's on a HDD are stored magnetically, a chunk of the magnetic medium aligned one way represents 1 and a chunk aligned a different way is 0. Over time, the alignment randomise on it's own (entropy) and the data is slowly compromised.
      A similar effect happens in SSD also. Here the data is stored as a charge on a the semiconductor. Over time, the charge WILL leak away thus compromising the data.
      The only way to prevent this is to have the drive plugged into a computer (be powered) and the integrity of the data is verified via checksum comparisons.
    P.S. I didn't read the link that jedishrfu posted. I apologise if what I said was already covered.
     
  5. Dec 29, 2014 #4

    Doug Huffman

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    SSD's have a r/w cycle limit. HDD are a known quantity commoditized and cheap. Assemble a RAID with plenty of spares.
     
  6. Dec 29, 2014 #5

    jedishrfu

    Staff: Mentor

    And be mindful of the UPS that you use or your raid will go up in smoke.
     
  7. Jan 6, 2015 #6

    harborsparrow

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    Umm. Well, there are those old threads about how to destroy a hard drive so that the data on it can never be recovered. Turns out it's not really all that easy. Data was read off one of the hard drives recovered from the crashed space shuttle (after it burned!). Of course, that doesn't mean that an average person can get the data, but experts could. If there is criminal evidence believed to be on a bad HDD, someone will find a way to read it. If it's just data you forgot to back up, no one will ever be able to read it.

    I don't really know about solid state.

    If you use a hard drive and back up to a second hard drive at reasonable intervals (or to the cloud), your data will be recoverable.
     
  8. Jan 6, 2015 #7
    But I'm talking about data over decades and more. I think that data is easy to erase when you let it sit over a very long time without using it. The question is, which data storage is better at long term storage (decades and more).
     
  9. Jan 7, 2015 #8

    harborsparrow

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    Oh. If it's any comfort, back in 2007 and 2008, I was retrieving data off floppy disks from the 1980's. Out of dozens, only one or two were unreadable, and that mostly from physical damage like having been bent.

    The problem with decades of storage is finding a machine and software to read them. For data stored that long, I'd put it in the cloud in multiple places, or move it periodically (say every 5 years) to something newer. Otherwise, I can't imagine any technology being still readable 20 years later. There is tape, of course, but very very unwieldy. Sorry, I may have nothing useful to say (other than the experience of hindsight, being old). I was staggered that the floppies had made it 20 years.
     
  10. Jan 7, 2015 #9

    jedishrfu

    Staff: Mentor

    One suggestion I was given was to use digital tape. The rationale was it was not scratchable like a cd and didn't suffer from warpage. While being tape it could b stretch d but being digital it could still retrieve the data. If I broke you might lose some but not all data and tapes were more resistant to magnetic fields. The field needs to be stronger than what would erase a diskette.
     
  11. Jan 7, 2015 #10
    Are there any digital tapes that can store tens of gigabytes of data?
     
  12. Jan 8, 2015 #11
    EEPROMs are often specified as having a 10-year data retention period. I have not found specs for Mask ROM and OTP. Mask ROM is more expensive beacause it is intended for thousands of copies, not just a few - however, it would certainly last for centuries.
    The last choices are OTP's. These are usually uvEPROMs with the memory sealed in a uv-blocking plastic. One 512Kbyte chip can cost about $7.50 plus shipping - and, of course, quantities would be cheaper. But their specified data retention is still only about 10 years.
    There are two other types of OTPs are fuse-link and anti-fuse. Both (especially fuse-link) would probably last for centuries, but the only parts I can find that use them are things like FPGAs or digital pots.

    Actually, I have some stored data that has lasted over 40 years without any noticeable degradation - and I expect that would last for centuries. The data is stored on punch card in metal bin holders. As long as they are dry and insect-free, they will last for quite some time.
     
  13. Jan 18, 2015 #12

    Svein

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    Yes. As of now there are two alternatives:

    DAT - the consumer-grade option. Useful for up to about 50Gbyte
    LTO - the industrial-grade version. There are several classes here, with LTO1 for up to 100Gbyte all the way to LTO6 for up to 2500 Gbyte.
     
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