Several misconceptions exist over how contesting technologies compare and contrast. One common one is that SSD, by having no moving parts, must automatically be more reliable and durable than HDDs. In actual fact, SSDs suffer from bit errors too and do wear out, more quickly than HDDs under heavy write loads. The write process causes most of the wear because it requires erasing memory cells and then rewriting each bit, with the resulting heat changes causing gradual deterioration of the oxide layer insulating the floating gate transistors. Cells are the building blocks of'SSD flash storage', each comprising a single transistor and capacitor to store charge, and are now predominantly arranged in NAND structures where they are connected in parallel. NAND has been preferred to the alternative NOR structure, where cells are connected in series, because it allows smaller chip areas for a given storage capacity. As a result the cost per bit is less and power consumption is lower.
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