Life Cycle of SSD - What you wish to know

With the Flash Memory Summit approaching next week, I thought it might be a good time to dig into the technology and life cycle of SSD. Unlike traditional hard drives, data storage on SSDs is not in the magnetic field, but rather within the flash memory chips (NAND flash). By design, the SSD is made with a motherboard, a few memory chips (depending on the size of the GB drive), and a controller that instructs the SSD.

SSD memory is a stable memory, in other words, it can store data without power. We can think of the data stored on NAND flash chips as an electrical charge stored in each cell. With that in mind, the question arises: longevity or SSD life cycle?

Flash memory impairment It is known that writing functions erode SSD memory cells, shortening their life. But will the memories all fade away in the same way?

The memory used for flash chips is not the same, there are actually three types of NAND:

SLC (Single Level Level Cell) - 1 piece of data per cell

MLC (Multi-Level Cell) - 2 pieces of data per cell

TLC (Three-Step Cell) or 3-bit MLC - three pieces of data per cell

You see: The more levels a cell has, the more pieces of storage space enter the cell, resulting in higher chip production. Thanks to modern technological advances we have an SSD that can store many GB and at an affordable price. Not surprisingly, a recent report shows that the TLC memory type should be approximately 50% of the total NAND grains by the end of 2015, with a production cost of about 15% - 20% less compared to the MCL layers.

But there is a downside: Adding more fragments to cells reduces their reliability, durability, and performance. It is very easy to determine the state (how much space) of an SLC cell, because it is empty or full, and it is very difficult to do the same for MLC and TLC cells as they have multiple regions. As a result, the TLC cell requires 4 times the writing time and 2.5 times the SLC cell reading time. When talking about the SSD life cycle, keeping multiple fragments per cell also means accelerating the wear of NAND memory.

The memory cell is made up of a floating gate transistor. It consists of two gates, a control gate, and a floating gate covered with a layer of oxide (you can see the formal representation on the right). Each time tasks are performed, e.g. to set and clear the cell, the oxide layer holding the electrons to the floating gate wears. As a result, as the oxide layer is weakened the electron channel from the floating gate is possible.

How long do SSDs last? This is a million-dollar question, obviously, it is impossible to give a direct answer but ... keep reading!

The practice of SSD is to focus on the production of products based on 3-bit MCL (TLC) memory. TLC memory is beginning to dominate the SSD market. In general, it seems that 2-bit MLC technology is more advanced in terms of durability and performance, let alone SLC's diminished demand and almost disappearing altogether. In other words, manufacturers are offering an extended life cycle to reduce costs to allow for the expansion of flash memory and their storage capacity.

However, there seems to be no concern about the length of the SSD. In a study conducted by The TechReport on 6 SSDs to understand how they can withstand writing tasks, 2 out of 6 drives have 2 PB data writing tasks and all tested SSDs can write hundreds of TB without problems.

Taking 2TB recordings per year, according to test results, the life expectancy of SSD can be as much as 1000 years (2PB = 2000 TB / 2TB year = 1000 years). Although we have a large amount of data written for them, we will be able to use our SSD silently year after year.