DRAM-less NVMe drives don’t have what basically amounts to a cache of readily accessible storage that makes large reads and writes faster. So they’re cheaper, but slower, and wear out faster

Some fancy SSDs have additional DRAM cache:

The presence of a DRAM chip means that the CPU does not need to access the slower NAND chips for mapping tables while fetching data. DRAM being faster provides the location of stored data quickly for viewing or modification.

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