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Why is RAM Disk so much faster than an SSD drive?

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closed as not a real question by Shane Madden, Chris S, John Gardeniers, ewwhite, Iain May 9 '11 at 7:54

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The same reason flying a jet is faster than walking from New York to Los Angeles. They're completely different technologies. –  Chris S May 9 '11 at 1:54

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It has to do with a number of factors. Bandwidth to memory vs SSD, also write latency speeds, DRAM is constantly refreshed and thus has a latency measured in nanoseconds, whereas Flash requires a high voltage to write into the gate along with a few other details, often SSD latency is measured in microseconds.

http://en.wikipedia.org/wiki/Solid-state_drive

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Great answer, so just suggesting an addition: an SSD has to pass through a storage controller, whereas modern chips have on-die MMUs, so (as a simple way to explain it, I know it's not a perfect analogy), RAM is "closer" to the CPU. Also, depending on what FS you're using, something like tmpfs writes marginally less data to the storage medium than does (f.ex.) ext3, since it's worried about crash recovery and is not journaling. –  BMDan May 9 '11 at 2:04

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