Reliability and life span of SSD drives?

Discussion in 'MacBook Air' started by nph, Dec 4, 2008.

  1. nph macrumors 6502a

    Feb 9, 2005
    I don't know too much about SSD drives so I am curious as to:
    1) What is the reliability?
    2) What is the lifespan compared to a regular HDD?

  2. hayduke macrumors 65816


    Mar 8, 2005
    is a state of mind.
  3. Anonymous Freak macrumors 603

    Anonymous Freak

    Dec 12, 2002
    I'll answer them in reverse.

    Depends on the exact model, but I calculated recently that with an "MLC" drive (higher capacity, slower write speeds, shorter lifespan,) you would need to write to it at maximum speed for about five years continuously to hit the predicted write cycles of the chips. For an SLC drive (lower capacity, faster write speeds, MUCH longer lifespan,) it would be measured in decades. For a conventional computer, you aren't going to be writing 70 MB/s nonstop 24/7 for years on end, so the predicted lifespan of the chips is much longer.* Explanation of SSD write-cycle lifespan below.

    There's a reason Intel's new SLC SSDs are marketed toward datacenter users. Extremely long lifespan, very good reliability.

    As for reliability, the lack of moving parts should help; all you have to worry about are power issues, and chip death. For a laptop, power issues should be erased, due to the "built-in power isolating UPS" nature of a notebook running off battery. And as for chip death, well, see above. * And below

    * Flash memory chips have a property where they 'wear out' as you write to them. Only writing wears them out, not reading. And each individual memory cell has a certain predicted number of writes it can take before dying. By estimates I have read, MLC should last about 100,000 write cycles; SLC about 1,000,000. Because it would be possible that you could try to use a drive such that it writes 1 MB, erases it, then writes that 1 MB again; SSDs have "wear leveling" algorithms where they won't actually write the second request to the same physical cells. They will effectively use up the entire drive's worth of cells before they re-write a single one. So you would have to re-write that 1 MB say, 64 thousand times before you even get to the SECOND write pass on a 64 GB drive. (128 thousand times on a 128 GB drive, etc.) Most SSDs also have more capacity of chips than they claim (For Intel's SSDs, it's about 25% more, I don't know about other manufacturers,) so even when the cells start to wear out; there are 'spares' to take their place for a while. (spinning magnetic hard drives also do this.) What this amounts to is that it takes a *LOT* of writes to wear out an SSD. For that 128 GB SSD, if you were to be able to write to it at 50 MB/s (a good estimate for most 128 GB SSDs out there,) continuously, it would take 42.6 minutes to completely fill. If it's the worse MLC drive, that comes to about 8 years of continuous write/erase/write to hit the 100,000 writes mark. For a faster SLC, you can write 3x faster, but you have 10x as many cycles, so it comes out to about 30 years. Of nonstop writing. Any reading is "free". If you write to it once, then read continuously, it should work "forever" (within the confines of reality, obviously.)
  4. Kan-O-Z macrumors 6502

    Aug 3, 2007
    I read somewhere today that Samsung is now boasting that it's SSD drives will outlast their owners....meaning it'll last longer than the average life of an adult! I'm not sure if that's so comforting to know!

  5. Anonymous Freak macrumors 603

    Anonymous Freak

    Dec 12, 2002
    To semi-quote myself: An SLC SSD being re-written at maximum speed won't hit it's rewrite limit for about 30 years.

    Assuming you "only" write at maximum speed 8 hours a day, you've just exceeded the average lifespan of a person.

    If you assume "standard business desktop computer" use, and write less than 5 GB / day, it will effectively last forever.
  6. arkhe macrumors newbie

    Nov 28, 2008
    Better and longer is about right


    I just replied to another thread ( with some info about SSDs that I found.

    In summary, the SSDs in the Rev 2 Air are designed to be more reliable than any comparable hard disk drive and to last at least as long as those same hard disk drives that they are replacing (ie. at least 5 year lifespan).

    YMMV, of course, but from everything that I've been able to research, they are both much more reliable (from a data integrity standpoint), and even in their mass market MLC variations, will probably last longer than the refresh rate of a mini ;-). Seriously, they should give you at least 5 years of good life before needing to be replaced.
  7. h1d macrumors regular

    Nov 30, 2008
    For stability, as already pointed out is supposed to be much better than HDD, but since SSD hasn't been around forever like HDD, probably due to its immature software/firmware, I doubt the stability is on par against HDD yet. There are many manufactures targetting SSD for servers lately, but I heard on another forum that one person put his Linux server on SSD, one day, he figured the machine was completely unresponsive, rebooted, found every data gone... :eek:

    Scared the hell out... But SSD will be the thing I'm sure, when manufactures sort out the disk space, life span, firmware and price it will ace HDD.

    At last raid 0 can mean something... (I laughed at someone doing 6 drive SSD raid0... but that is a bit too much though.)
  8. agurlnamedgoo macrumors member

    Dec 3, 2008
    Man... when I go down... I wanna leave something cryptic buried in the ground on an SSD. What would people think?!

    (sorry... I get weird when it's late)
  9. Ironic macrumors 6502a


    Oct 6, 2008
    In my MBA!
  10. h1d macrumors regular

    Nov 30, 2008
  11. johny5 macrumors 6502a


    Mar 31, 2007
    Installed an OCZ 120gb SSD into my unibody 2.4 Macbook and am loving the speed.
    Had LOTS of hiccups with XP in vmware but this was fixed after many changes to XP (basically XP was written with lots of caching in mind so all of this had to be disabled!)
    Anyway, everything is great now! apps open up mega quick in OSX :p
  12. sychee macrumors member

    Dec 7, 2008
    What if I purchase videos off iTunes Store (say 10 episodes/day). Each video is about 700MB in size. Now, how long will my SSD lasts?

    Is our SSD Solid State Drive a SLC or MLC?

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