The data is stored in the form of an electric charge inside the NAND Flash cells (floating gate transistors) of Solid State Drives. An electric current is required for almost every task inside your solid-state drive. The faster the flow of electric current, the more will be the heat generated due to the interference of electrons.
As the workload increases on the drive, the amount of electric current required to do the tasks increases as well. This is because everything inside an SSD including host communication, storage of data, creating mapping tables, running algorithms, etc are done with the help of electronics and electric energy. Wherever any component uses energy, heat will be generated as a byproduct.
Heavy workload means moving heavy files for a large amount of time or working with random data even for a short duration of time.
The transistors that store the data need to be switched on or off and the frequency can be very high depending on the data in hand. This quick switching also generates a lot of heat. So, this all comes down to the fast read/write speed of SSDs. This is the reason why Gen 5.0 drives are generating a lot more heat as compared to Gen 4.0 drives.
The fast speed of data storage, retrieval, removal, and organization inside solid-state drives needs a faster flow of electric current. This quick flow results in excessive heat during heavy workloads.
The real reason for heat
Most people see their data as photographs, videos, texts, files, etc. But, engineers understand them in the form of bits. To store a 1MB data file, there could be billions of bits need to be stored. For electronics engineers and circuit designers, the bits 0 and 1 further translate to the transistor’s condition at a point. To store a bit value of 0, the FGMOSFET should have a charge stored inside its floating gate. If bit value 1 is required, the transistor must be free from any charge at its floating gate.
When billions of transistors come into play and the process of storing and reading data is automated with the help of fast processors, these circuits become our storage drives.
But, at the end of the day, there is always an FGMOS that is holding your data in the form of a single or multiple bits.
To insert the charge inside this floating gate, it must bypass the dielectric layer. This layer will keep the data there when there is no power input. But, for the initial storage, the charge must be pushed with an excessive force called electron injection. This extra push is one of the main reasons for heat generation. When these operations are more, the total heat will be more.
Next, because all these tasks are controlled by a controller, it needs to work with a lot of resistance and switching mechanisms. This is our second reason for the heat. Again, when the workload is high, the controller will be put under a higher load.
What SSD components heat the most?
SSD controller and the NAND Flash memory chips generate the most amount of heat during heavy read/write operations. The controller has got all the tasks from communicating with the host to arranging appropriate locations for data storage. It also has the responsibility to prepare the data tables and keep them safe so that the data can be retrieved easily when required. All other software components such as garbage collection, wear leveling, etc are handled by the controller.
The Flash memory doesn’t get very hot in normal operations. Random read/write operations put the most amount of load on the flash memory as compared to the sequential operations. However, this happens gradually and takes a long time because not all the pages inside the flash memory are written altogether.
DRAM chip on the SSD can also become hot when the write load is high. It serves as an intermediatory between the host and the NAND flash keeping the heavy flow of incoming data organized.
What type of tasks generate the most amount of heat in SSDs?
Random read/write operations generate the most amount of heat because of the excessive load on the flash transition layer. Between these, random write operations are the most demanding operations in terms of electronics. The small chunks of data need to be stored in separate locations and the number of mapping tables also increases.
The amount of wear leveling and garbage collection also increases when it writes the random data.
Also, when your SSD starts to get fuller, especially over 60%, the algorithms like garbage collection, error correction code, TRIM, and wear leveling start to put extra load on the components.
Encryption in SSDs adds an extra layer of process during the data storage contributing to the overall heat a little more.
The real reasons SSDs get hot?
According to the law of conservation of energy, the energy consumed is converted into work and heat. In the context of SSDs, the electrical energy consumed by the device is transformed into two primary forms: work (reading, writing, erasing, and processing data) and heat (a byproduct of these operations).
The NAND Flash cells need a high amount of charge to surpass the threshold voltages. For storage of charge, there must be high energy to go through the dielectric. Inside the controller, the active components i.e. transistors will have a capacitive load that consumes a lot of power.
No matter what I say to explain this to you, this all has to come down to the basics of physics. To make any circuitry do anything, there must be some kind of resistance. Resistance always results in heat. It is like a barrier for the current and voltage so that we can decrease it. This reduction in current and voltage is done by converting it into heat. When we talk about the SSDs, the transistors that store the data bit by bit need
NAND Flash Memory Operations
NAND flash memory cells require electrical charge to store and retrieve data. Even when the data is erased, some energy is required to drain the charge into the ground. The process of programming (writing) and erasing data in NAND cells involves moving electrons across a dielectric barrier, which is a high-energy process. The energy required to perform these operations, especially during large-scale data writes or erases, contributes to heat generation.
Semiconductor Physics and working of transistors
SSDs store data inside floating gate transistors. These transistors are embedded in integrated chips and a 1TB SSD can have billions of these transistors. The bit/bits of data are stored and recognized by the position of these transistors.
Generally, the presence of charge in a transistor in an SLC SSD is considered logic 0 by the controller and no charge as logic 1. By combining these bits in a huge number, the data is kept safe. Because these transistors can hold the data even without the power, the whole data will stay there.
The heat is generated when the transistor is turned On and Off rapidly. Since a transistor is made up of a semiconductor, it partially resists the flow of current. This resistance results in heat. So, as this switching of the transistor increases and goes on for longer periods, the NAND Flash chips get hot.
However, engineers design these chips to withstand a pretty good amount of heat. SSDs can reach up to 90°C and can stay pretty safe. All SSD controllers also have the mechanism for thermal throttling. This simply decreases the performance of your drive just to reduce the heat so that the SSD doesn’t burn itself by an overload.
Controller Operations and heat generation
The controller is generally the primary reason for heat inside the SSDs. Because the controller acts as the processor handing all the requests from the host and storing the data inside the flash cell, it is supposed to get hot a lot.
The main components of any SSD controller are the processor, flash transition layer, DRAM, NAND flash, host interface, and power management unit. The most power-consuming part of the controller is its processor, also called the CPU core. After that, the DRAM cache and NAND interface are the most common heat-generating components.
The controller is made to withstand a pretty high range of temperatures even without throttling. However, the constant and heavy load can make the controller slow.
When I say constant and heavy load, I am talking about the tasks having 50 to 100 GB and even bigger sizes of data. Normal copy/pasting, gaming, video editing, moving video files, and other related tasks aren’t considered heavy on SSDs.
Conclusion
Heat is a very normal phenomenon in solid-state drives. Also, they are equipped pretty well to handle this heat. The components are designed to reach 80°C even without throttling. A little cool air in your CPU case is enough to keep it working for hours without any issues. Heat can become dangerous when it is there in idle conditions.