Size
Nominal drive capacity. This parameter directly determines not only the amount of data that can fit on the device, but also its cost; many SSD models even come in several versions that differ in capacity. Therefore, when choosing, it is worth considering the real needs and features of the application — otherwise you can overpay a significant amount for volumes that are not needed in fact.
In terms of actual values, a capacity of
120 GB or less is considered small these days. This can also be equated with
a 240 GB SSD. Average values are already considered
500 GB, increased —
1 TB(in the range of which
SSDs fall 400 and
800 GB). And the most capacious modern SSDs can accommodate
2 TB,
4 TB and
even more.
Controller
Model of the controller installed in the SSD.
The controller is a control circuit, which, in fact, ensures the exchange of information between the memory cells and the computer to which the drive is connected. The capabilities of a particular SSD module (in particular, read and write speed) largely depend on this particular scheme. Knowing the controller model, you can find detailed data on it and evaluate the capabilities of the drive. For simple everyday use, this information is usually not needed, but for professionals and enthusiasts (modders, overclockers) it can come in handy.
Nowadays, high-end controllers are produced mainly under such brands:
InnoGrit,
Maxio,
Phison,
Realtek,
Silicon Motion,
Samsung.
Shockproof
A parameter that determines the resistance of the drive to drops and shocks during operation. Measured in G — units of overload, 1 G corresponds to the usual force of gravity. The higher the G number, the more resistant the device is to various kinds of shocks and the less likely it is to damage the data in it, say, in the event of a fall. This parameter is especially important for external drives (see Type).
MTBF
The drive's time between failures is the time that it is able to continuously work without failures and malfunctions; in other words — the operating time, after which there is a high probability of failures, and even failure of the module.
Usually, the characteristics indicate some average time derived from the results of conditional testing. Therefore, the actual value of this parameter may differ from the claimed one in one direction or another; however, in fact, this moment is not particularly significant. The fact is that for modern SSDs, the MTBF is estimated at millions of hours, and 1 million hours corresponds to more than 110 years — while we are talking about pure operating time. So, from a practical point of view, the durability of a drive is often limited by more specific parameters — TBW and DPWD (see below); and the manufacturer's warranty generally does not exceed several years. However, data on the MTBF in hours can also be useful when choosing: other things being equal, more time means more reliability and durability of the SSD as a whole.
Write IOPS
The IOPS provided by the drive in write mode.
The term IOPS refers to the highest number of I / O operations that an SSD module can perform per second, in this case, when writing data. By this indicator, the speed of the drive is often evaluated; however, this is not always true. Firstly, the IOPS values of different manufacturers can be measured in different ways — by the maximum value, by average, by random write, by sequential write, etc. Secondly, the benefits of high IOPS become noticeable only with some specific operations — in in particular, the simultaneous copying of numerous files. In addition, in fact, the speed of the drive may be limited by the system to which it is connected. In light of all this, it is generally acceptable to compare different SSD modules by IOPS, but the real difference in performance is likely not to be as noticeable as the difference in numbers.
As for specific values, for the write mode with IOPS
up to 50K is considered relatively modest,
50 – 100K — medium,
more than 100K — high.
Read IOPS
The IOPS provided by the drive in read mode.
The term IOPS refers to the maximum number of I / O operations that an SSD module can perform per second, in this case, when reading data from it. By this indicator, the speed of the drive is often evaluated; however, this is not always true. Firstly, the IOPS values of different manufacturers can be measured in different ways — by the maximum value, by the average, etc. Secondly, the advantages of high IOPS become noticeable only with some specific operations — in particular, when copying numerous files at the same time. In addition, in fact, the speed of the drive may be limited by the system to which it is connected. In light of all this, it is generally acceptable to compare different SSD modules by IOPS, but the real difference in performance is likely not to be as noticeable as the difference in numbers.
For modern SSDs in read mode, an IOPS value of
less than 50K is considered a very limited indicator, in most models this parameter lies in the range of
50 – 100K, but there are also
higher numbers.
DWPD
The number of full overwrites per day allowed by the design of the drive, in other words, how many times a day the entire drive can be guaranteed to be overwritten without fear of failures.
This parameter describes the overall reliability and durability of the drive. It is similar in meaning to TBW (see the relevant paragraph), one value can even be converted to another, knowing the warranty period: TBW = DWPD*V*T*365, where V is the drive capacity in terabytes, and T is the warranty period in years . However, DWPD is somewhat more specific: it describes not only the total time between failures, but also the limit on the number of rewrites per day; if this limit is exceeded, the drive may fail earlier than specified in the warranty. However, even small DWPD values —
0.5 – 1 time per day, or even
less than 0.5 times a day — often turn out to be sufficient not only for simple everyday use, but even for professional tasks. Higher rates —
1 – 2 times a day or
more — are rare; at the same time, it can be both high-end and low-cost SSD modules.
