Technology and Life Cycle of SSD
With the Flash Memory Summit coming up next week, I thought it would be a good time to take a look at the technology and life cycle of SSDs. Unlike traditional hard drives, SSDs store data on flash memory chips (NAND Flash) rather than magnetic fields.
By design, an SSD is a motherboard, with a controller that provides instructions for the SSD (depending on the size of the drive-in GB) and the SSD.
SSD memory is static memory, in other words, it can store data even when it is not running. We can assume that the data stored on NAND flash chips is in the state of electrical charging stored in each cell. With this in mind, the question arises: how long is the SSD lifespan or life cycle?
Flash memory violation
Writing work SSD shortens the life of memory cells, thereby shortening their lifespan. But do all memories end like this?
The memory used for flash chips is not the same, there are actually three types of NAND:
- SLC (Single Level Level Cell) – One-bit data per cell
MLC (Multi-Level Cell) – 2 bits of data per cell
TLC (Triple Level Cell) or 3-bit MLC – three bits of data per cell
- As you can see: the higher the level of the cell, the more bits stored in the cell, resulting in more powerful chips. Thanks to modern technological advances, we have SSDs that have less GB and are more affordable. With 15% – 20% lower production costs than MCL chips, it is not surprising that a recent report suggests that TLC memory types should handle 50% of all NAND chips by the end of 2015.
However, there is a downside: adding more pieces to the cells reduces their reliability, durability, and performance. Determining the location (how much space) of an SLC cell is easy because it is empty or full, but it is very difficult to do in MLC and TLC cells because it has so many areas.5 times the reading time. When discussing the SSD life cycle, storing multiple bits per cell means accelerating the aging of NAND memory.
The memory cell is designed with a floating gate transistor. It consists of two gates, a control gate and a floating gate coated with an oxide layer (you can see the schematic representation on the right). Activities to be performed, e.g. Damage to the system and the cell is caused by the deterioration of the oxide layer that holds the electrons in the floating gate. As a result, as the oxide layer weakens, the release of electrons from the floating gate becomes possible.
This is a question of millions, clearly not straightforward but … keep reading!
The practice of SSDs is to focus on developing products based on 3-bit MCL memory (TLC). TLC began to dominate the memory market for SSDs. With regular use, 2-bit MLC technology seems to be powerful in terms of durability and performance, apart from the declining demand for SLC and its almost complete disappearance. In other words, manufacturers are offering less flash memory and an extended life cycle to allow cost to extend their ultimate capacity.
However, there are no concerns about SSD length. In a study conducted to understand how techriport 6 SSDs cope with write tasks, 2 out of 6 drivers perform 2 PB data writing tasks and not all SSDs are tested. They were able to record hundreds of uninterrupted TBs.
According to test results, for 2TB of writing per year, the lifespan of an SSD is estimated to be equal to 1000 years (2PB = 2000 TB / 2TB years = 1000 years). Even with the growing data designed for them, we are able to use our SSDs silently for years and years and years.
Replacing the standard magnetic hard drives in today’s computers, solid state drives are based on the same memory technology used in digital cameras. What these devices have in common is that they both store information using flash memory chips. SSDs are essentially a series of memory chips with built-in logic boards. The advantages of this technology are faster speed, lower power consumption, and durability.
The working principle of the SSD is a lot similar to a USB drive or an SD card. Data is stored into blocks that can be written and deleted just like files. Each block is composed by a number of cells where one bit per cell means 0 and two bits per cell means.
- The cells are interconnected with word lines, which define the values of each bit, and bit lines, which define how many bits per cell do they contain. For example, to represent a 1 bit per cell (a single flash memory chip), you connect the wordline and bit line. To represent.
2 bits per cell (two chips), you connect the wordline and two bit lines. The current can not pass through these cells so they are used to represent 0 and 1, but in practice the encoding is more complex than this simple example.
Companies such as Intel or Micron Technology produce both the memory chips and the logic boards of the SSDs. The amount of bits stored on a single memory chip varies depending on the type, but for consumer products between 256 and 4,096 Gb per chip is common.
To provide a more familiar reference to users, SSDs are divided by their storage capacity into different “Series”. The difference between one Series and another is given by the number of bits stored per cell, with each Series doubling the capacity of the previous one. For instance, Series 6 means that each memory chip has 6 bits per cell (2 to the power of 6) while Series 8 doubles this number (2 to the power of 8).
As you might expect, higher capacities are not achieved by using larger chips but instead by stacking more of them on each other. To do this, the storage device has to be partitioned into more than one block of memory, meaning that you can’t add a single chip and double the capacity of your SSD at home without risking corrupting all your data. For cost reasons it’s also not possible to mix different Series chips on one product, so there are only a few possible configurations of SSDs.
The Series 2532B, employed on the Intel X25-M for instance, have a capacity of 32 Gb per chip and double each time you go to a higher Series number (4 chips per block * 2 bits per cell).
Theoretically this means that it’s possible to store up to 2048 Gb (2 to the power of 20) on a Series 2532B SSD (256 Gb per Series). In practice, however, other limitations such as maximum read and write speeds and the number of available chips make it impossible for manufacturers to go this far.