Unallocated Space on SSD

Discussion in 'Hardware Components and Aftermarket Upgrades' started by DaysEnd, Feb 3, 2013.

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  1. DaysEnd

    DaysEnd Newbie

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    Hi, I just bought an intel 180GB SSD and while creating the partitions I accidently left 20GB of unallocated space.

    Is it okay to leave the space there? I'm worried about unevenly wearing the SSD
     
  2. jclausius

    jclausius Notebook Virtuoso

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  3. yalcin19

    yalcin19 Notebook Consultant

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    That unallocated space you left will be treated as spare area. And it will increase endurance.
    If it was me, I would have left 36Gb unallocated .
     
  4. OtherSongs

    OtherSongs Notebook Evangelist

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    He's likely OK with 20GB unallocated with a SSD with nominal 180GB of space; that's 11% unallocated together with whatever spare space the SSD already has set aside.

    An odd nominal size of 180GB likely has unstated spare area set aside.

    I'll like SSD drives a whole lot better when they start stating upfront how much spare space is set aside as unallocated space!!!
     
  5. yalcin19

    yalcin19 Notebook Consultant

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    He is OK with that, no probs.
    Again. if it was me, I would have left 32Gb unnallocated for 180Gb that is 17% + (probably 6.88% reserved for spare area).
     
  6. tilleroftheearth

    tilleroftheearth Wisdom listens quietly...

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    In either a same (capacity-wise) free space or 'unallocated' condition: sure all nand will be used.

    The difference is that in a simple free space setup; all the nand will be 'dirty' at almost all times. This will give the dreaded read/update/erase/write cycle that not only needlessly burns through the nand cycles (increased Write Amplification (WA), but also gives the lowest and most inconsistent performance the SSD (controller/nand combo) can give.

    While in the 'unallocated' setup; the nand will be cleaned, primed and ready to work (at our command) giving the most performance possible with the least WA.


    The thing to remember about over-provisioning is not that it increases the performance of the storage sub-system (even if it does in terms of consistency) - but rather that it prevents the SSD from going into an out-of-control tail-spin that only a SE (secure erase) would be able to make it perform at the speeds it is capable of.


    In my experience (even if Anand recommends at least 25%) - I have found that 30% over and above any other built-in spare area/over-provisioning is the best balance of capacity 'lost' vs. performance gained.

    This is the calculation I use to find that 'magic' 70% of any SSD's capacity:

    Example SSD 'nominal' capacity: 180GB...

    180 x 1000 x 1000 x 1000 = 180,000,000,000 bytes (advertised capacity).

    180,000,000,000 / 1024 / 1024 / 1024 = ~167GB actual capacity available.

    167 x .7 = ~117GB actual capacity available with 30% over-provisioning accounted for.


    Note:
    To get more accurate numbers; use the total MB's available in the Windows 7 or Windows 8 custom setup (drive) options - not that this matters, but SSD's just like HDD's are not all 'equal' with how much actual available space is shipped. What the Win7/8 setup options show is the actual available for your drive - take that number and multiply it by 0.70.




    While it is true that an SSD's controller will ensure that ALL nand chips be used as equally as possible (whether in a used, free space or 'unallocated' state) and therefore it can't 'wear' unevenly - it is also true that 'unallocated' capacity is superior to simple 'free space' when WA, GC TRIM and sustained, performance over time (consistency) is also taken into consideration.
     
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  7. OtherSongs

    OtherSongs Notebook Evangelist

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  8. DaysEnd

    DaysEnd Newbie

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    Thanks for all the informative replies. I'm glad now that I left some space when partitioning. 70% gives me plenty of space for programs and games and I shall keep all data and media in my HDD.
     
  9. J.Dre

    J.Dre Notebook Nobel Laureate

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    The disk management utility should allow you to take advantage of that space. If not, don't worry, it's not harming anything.
     
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