What is the difference between SSD, Flash Memory, NAND, DRAM, RAM etc.?

Here's a very quick distinction.

Flash memory -- Storage medium

NAND -- a type of flash memory (specifically, a type that can retain data without power)

SSD -- solid state drive, uses NAND type of flash memory

RAM -- Random Access Memory. Volatile, meaning the data is lost when power is lost.

DRAM -- Dynamic RAM, a broad term for various types of RAM

If you want more details into the uses for each, that will take me a bit longer to type.

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Well, a solid state drive just has no moving parts, so the underlying tech that makes it work is irrelevant.

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He may be wanting to know about their performance advantage as a storage medium, and why the lack of moving parts means anything other than reliability (i.e., nothing that wears out/breaks mechanically).

For example, with no read/write heads to seek data blocks on a moving platter, SSDs have tremendously superior access and transfer times compared to hard drives. If your operating system needs to access data on an SSD, it does not have to wait for the data to be found. The data is always there and waiting for your operating system. Much of the everyday noticeable speed increase comes from its random read/write performance with small file blocks and a queue depth of 32. In other words, there can be 32 read/write requests pending at any given time, allowing an SSD to handle multiple read/write requests in parallel, and this improves random read/write speeds dramatically. Individual hard drives don’t have this capability.

The effective use of flash memory in SSDs stems from the drive's controller/processor that allows the NAND to interface with the rest of the PC and OS. The controller is responsible for caching, correcting errors, block mapping, wear leveling, and a few other things that escape me at the moment.

There's also the topic of flash memory having a finite number of writes. There is some misinformation out there about the reliability and lifespan of SSDs. Ultimately, what turns people off is the fact that SSDs are often advertised with a finite lifespan. It’s true; the flash memory in SSDs can only be erased/overwritten so many times before the memory blocks begin to degrade and slow down. Depending on the type of NAND it uses (SLC, MLC, or TLC), SSDs have a threshold of 1,000–100,000 write cycles, with the upper limit requiring a more expensive type of flash memory.

To measure this in terms of years, I’ll use my own situation as an example. I have a Samsung 830, an SSD that has since been discontinued in favor of Samsung’s new 840 models. After a year of heavy use (my computer is on 24/7 and actively used for at least 8 hours a day), I reached about 60 write cycles. At this rate, assuming a minimum write cycle threshold of 1,000 (it’s actually much higher in a Samsung 830 because of the NAND type it uses), I would have 16 years of write cycles left! Most people don’t keep storage devices for even 5 years, but there is enterprise-level SLC NAND to withstand 100 times that amount of write cycles.

The irony of this SSD lifespan stigma is that people seem more willing to accept the nature of hard drives, which can last 15 seconds or 15 years and will most likely fail without warning somewhere in between. Yet SSDs, simply because we’re told up front that they don’t last forever, are viewed as a scary and volatile storage solution.

Years ago, buggy controllers and firmware sometimes caused SSDs to fail or dramatically reduce in performance before the flash memory was exhausted, but today’s SSDs have improved dramatically (as technology tends to do).

I really should be paid (probably by Samsung) for as much as I promote SSDs.

Enterprise-level hard drives last a long time, except when they don't.