Analysis of how much capacity of an SSD is the best deal

People often come to ask me about how much capacity of an SSD is the best deal to purchase. Most of the time, I will recommend the SSD of 240G.

Is the 240G SSD sufficient for daily use?

When the SSD was first introduced, the smallest SSD was 60G. For this type, there was no extra space to use after installed the operating system. Now, basically there are no such small SSD on the market, even the smallest one is also 120G. For 120G capacity, there are still space for 1~2 large games after installed the operating system. This type SSD can satisfy the basic needs of a household, but its price has no advantage. The life of SSD is limited, especially the latest type of hard disk with TLC particles, which has a life cycle of less than 1000 times. Therefore, after it being repeatedly read and wrote over 1000 times by occupying memory space, its life may come to an end, which may have a big impact on data security and usage period.

If we use the 120-128G version of the SSD, then this life cycle will be reached very quickly. Normally, the system and commonly used software may occupy a large part; not to mention that we may too careless to pay much attention on repeatedly storing and organizing all kinds of information. The life of the 120G SSD is less than the 240G SSD, so it is not recommended to choose 120G. I recommend you choose an SSD with more than 240G capacity. Therefore, SSD with more than 240G capacity is the most cost-effective and safe choice.

Currently, the 240G SSD is neither too small nor not too large. After all, now mechanical hard drives have a capacity more than 1TB.
Then, is the 240GB SSD sufficient? Let's first take a look at the 240GB SSD in below pictures to see the actual available capacity.
Because there are different the manufacturer and different computer capacity calculation methods, and the firmware inside the SSD also needs to occupy storage space. Therefore, the actual usable capacity of the 240GB SSD we purchased is about 223GB.

Capacity demand factor:

Whether it is a solid-state disk or a mechanical hard disk, it should not be occupied too full. If the mechanical hard disk is too full, it will intensify the fragmentation of the hard disk. However, the remaining space reserved by the solid-state disk can be regarded as the OP capacity when the Trim is turned on. This way can improve garbage collection efficiency, facilitate wear leveling and reduce write amplification. The 240G SSD is obviously better than the 120G SSD after including the consideration of a reasonable remaining space.

Performance factors:

As the storage density of flash memory continues to increase, the price per unit of flash memory is decreasing gradually. But there are also some contradictions for small-capacity solid-state drives: the increase in single-die capacity leads to the decrease in the number of CEs, which will affect the continuous write performance of the small- capacity SSD. There will also be an impact of the SLC cache capacity on the TLC flash SSD. For example, the SLC cache capacity of the Toshiba Q300 120G is about 2.2GB. After the cache is used up, the write speed is about 95MB/s. Whereas for the 240G model, SLC cache is increased to 3.4GB. After the cache is used up, the write speed is increased to about 175MB/s. It is obvious that 240G has great improvement in performance compared to 120G. From the perspective of Cost-Performance ratio, it is undoubted that the 240G model is a better choice.

Price factor:

I recommend 240GB instead of 120G with considerations of not only the requirement for larger capacity but also the price. Take the Toshiba Q300 as an example. The price of 120G on Amazon is $88, while the 240G doubles the capacity of 120G, but the price has only increased by more than 30%, which is $108. The price of 480G is less than twice that of 240G, which makes 480G has the lowest price per unit of all capacity models.

Some friends may ask, they are the same in having both a master and a flash memory, why the price of 480G model can be lower than two 240G models? This is because 480G model saves the cost of a master compared to two 240G models, and the cell number is also different. The following is the picture of a dissembled 240GB Toshiba Q300 for comparison:

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