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Ubuntu 12.04 LTS - Benchmarking All The Linux File-Systems

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  • #21
    And what about partitions? I suposse it just work inside every partition asigned sectors. So would be better to make bigger than needed partitions and don't make swap ones in SSDs.

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    • #22
      Originally posted by malkavian View Post
      And what about partitions? I suposse it just work inside every partition asigned sectors. So would be better to make bigger than needed partitions and don't make swap ones in SSDs.
      The wear levelling is done on the hardware side, so it doesn't really care about your partition/filesystem layout. What happens is that it keeps a table of "what the system thinks is block 1234 is currently on chip 3 offset 0010" and so on for every physical block, and then it's free to cycle which physical positions it uses. Imagine a rewrite: Instead of reusing the same block, it can take an unused block, write the new content there, update the "this is there"-table, and put the old block at the end of the queue of free ones. (I imagine it works better with TRIM support, since that lets the disk consider much more space as "free". )

      It's the same translation map idea that is used for virtual memory.

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      • #23
        Quoth wikipedia:
        MLC NAND flash used to be rated at about 5–10k cycles (Samsung K9G8G08U0M) but is now typically 1k - 3k cycles

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        • #24
          Originally posted by curaga View Post
          Quoth wikipedia:
          Right, that's a bit annoying. The chips in the intel 320 series are apparently rated at 5k - so halve the above numbers. On the flipside, lager capacities help - so newer models will make up for it just by having more space to spread the writes over.

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          • #25
            Originally posted by dnebdal View Post
            Right, that's a bit annoying. The chips in the intel 320 series are apparently rated at 5k - so halve the above numbers. On the flipside, lager capacities help - so newer models will make up for it just by having more space to spread the writes over.
            Larger disks only help if you're not actually using the space. And if that's the case, why pay for a big ssd in the first place?

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            • #26
              Originally posted by curaga View Post
              Larger disks only help if you're not actually using the space. And if that's the case, why pay for a big ssd in the first place?
              As long as the absolute amount of free space is larger, it helps. Larger drives tend to both have more reserved space and for the user to leave (in absolute amounts) more free.

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              • #27
                I'll have to counter that with Murphy's law, the steady state of any disk is full

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                • #28
                  Originally posted by curaga View Post
                  I'll have to counter that with Murphy's law, the steady state of any disk is full
                  Better stated as a gas law, I think - stored data expands to fill all available space.
                  (Still, if you do a programs / data split over an SSD and a normal disk, it often works out with some free space on the SSD.)
                  Last edited by dnebdal; 03-17-2012, 05:05 PM.

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                  • #29
                    Well, just read in wikipedia and with static wear leveling free or used space is not a problem: http://en.wikipedia.org/wiki/Wear_leveling#Types

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                    • #30
                      Originally posted by malkavian View Post
                      Well, just read in wikipedia and with static wear leveling free or used space is not a problem: http://en.wikipedia.org/wiki/Wear_leveling#Types
                      Ah, that's fairly elegant.

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