There are two different types of ssds, the single level cell (slc) and the multi level cell(mlc), the latter being the norm for typical consumer use mainly because of its cost. The slc ssd is preferred for high efficiency server systems, more expensive and is expected to have a much longer lifespan than the mlc ssd. A typical mlc ssd is expected to last for 10, 000 write cycles whereas the slc is expected to last for 100, 000 write cycles.
So how long is 10,000 write cycles? It is not really a calculation we need to concern ourselves with but the average ssd is expected to last 1.5 million hours before failure. That is somewhere in the area of 173 years.
A quick background of computer systems reminds us that computers interact through their own language known as binary code. Binary code is a very simple language where everything is represented by 2 numbers, ‘0’ an ‘1’. Each letter of the alphabet is represented in binary code as 8 digits. For example, the letter ‘A’ in binary code is actually ‘01000001’. In a slc ssd, a cell consists of 2 digits (01) whereas in a mlc ssd, it consists of 4 digits (0101).
I know it gets confusing but, it is much easier to maintain and control a cell with two states (01)such as the slc than it is with multiple states(0101) as in the case of the mlc. I guess a better way of explaining is that a machine with 5 moving parts is going to be more reliable than the same machine with 10 moving parts.
Having a grasp on this, we can see how the reliability of the slc ssd is so much higher than that of the mlc ssd but, does it really matter when we are looking at a lifespan in excess of 150 years in any case?
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