I see nothing surprising about your 15k drives writing faster than the SSD. Flash memory is slow writing. Internally, NAND flash memory it is page oriented (pages>sectors). So to write a sector the SSD reads the page, replaces 512 bytes, erases the page, and finally writes the page.
Your tests are totally sequential. Your write test is a load via a dump, and your read test is ‘SELECT *…’. The real strength of SSD drives is their random read speed. Your test is not forcing the 15k HD to seek often, so what you are really testing is just the interface speed.
I don’t understand it.
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