How to choose the SSD?

Latest modification: 4 September 2018

Why your computer needs a SSD?

Installing an SSD on your computer is undoubtedly one of the best improvements you can invest in to significantly improve performance and achieve unprecedented comfort. However, as with any new technology, it will take a long time for potential users to understand the benefits of this investment that seems to be costly at first glance.

An additional difficulty when choosing the right SSD is the product variety, which is growing with every day. The number of available products and parameters, multiplied by the number of different applications for which we purchase SSDs, makes choosing such products a real challenge for many of us. 

What is actually an SSD and how does it differ from a classic hard drive? 

Solid State Drive (SSD) is a type of storage used to store data on our computers. Until recently, only traditional hard disk drives (HDDs) played such a role, however, due to the dynamic technological advancements over time it turned out that such an old technology does not meet the requirements set by today’s digital world.

Traditional HDDs store data on drives (platters) using a moving head for recording. Simply put, every time we want to access our data, the head moves across the surface of a rotating disk, searching for the data we are interested in. An average hard drive can perform about 100 read/write operations per second (IOPS), and data access takes up to 15 milliseconds.

The SSD, on the other, lacks any moving elements which are replaced by NAND flash, allowing up to 100,000 read and write operations per second. This also limits the time needed to access the data to over 100 times (to 0.1 milliseconds).

Differences in design have a number of other advantages as well. The lack of moving parts makes SSD much more robust to physical damage, minimizing the risk of data loss in the event of a shock or fall. SSDs are also significantly more energy efficient, which has a direct impact on extending laptop battery life.

An additional advantage of using flash memory is the ability to significantly reduce the physical size of the drive compared to the traditional 3.5″ or 2.5″ format that is usually associated with hard drives. Due to the flexibility of component placement, the SSD surface can be up to 90% smaller than a traditional hard drive. This makes it possible to mount the drive even in the thinnest ultrabooks or all-in-one desktops, which can accommodate the entire build in a monitor enclosure. 

What is the difference between SSDs?

Each SSD has a number of features and parameters that determine its intended use. They affect performance, reliability, compatibility and ultimately price. So how to choose an SSD that will meet our expectations and at the same time will not burden our home budget?

The basic parameter that should be considered when purchasing the SSD is its form factor and interface. Currently, more than 95% of SSDs sold in stores are available in 2.5″ format with a SATA III connector. Since this standard has been around for a long time, it allows for simple migration from traditional hard drives, which are mostly available in this form factor, while providing faster than satisfactory performance. An additional benefit of the SATA interface is its compatibility with older generations (also called backward compatibility). SSD with SATA III interface can be installed in a computer with SATA II or SATA I interface without any worries. This means that SSDs can be successfully installed even on computers that are more than 14 years old – that’s how long it has been since the SATA standard was launched. However, it is worth remembering that due to lower throughput of SATA I and II interfaces (150 MB/s and 300 MB/s respectively), connecting a new SSD to an older computer may limit its speed.

Another feature that should be considered when selecting the right SSD is its form factor. Most 2.5-inch drives have 7mm chassis thickness. Due to the fact that many laptops (especially older ones) have mounting bays for 9.5mm thick drives, it is a good idea to verify that a spacer is included with the drive before purchase. It will guarantee compatibility regardless of the bay depth (7mm or 9.5mm). The most common SSD is the one with a 2.5″ SATA connector, 7mm slim.

SSD performance 

Another parameter, which many consider to be the most important, is the drive’s performance. It determines how quickly our computer will respond to our requests and affects the overall convenience of using the computer and the comfort of everyday work. Performance is expressed by many different parameters with two of them being the most commonly specified. The first one, which determines the speed at which our disk will perform operations on files, is the speed of the disk expressed in megabytes per second (MB/s), determined separately for reading and writing. Today’s SATA III-based SSDs enable a transfer rate of 500MB/s, up to 5 times higher than hard drives with the same interface. The latest PCIe based SSDs with NVMe interface are even faster, reaching speeds up to 2.5GB/s. This speed will be especially appreciated by professionals, but for the majority of users the SATA III speed will be completely satisfactory.

The next parameter – the number of input/output operations per second (IOPS) – indicates the number of operations our drive can perform in one second. As with speed, the IOPS parameter is specified separately for reading and writing data. The average SATA III-based SSD achieves an IOPS of 50000 and the fastest drives can process up to 100,000 operations per second. By comparison, today’s hard drives for consumer use will only perform 100 operations per second.

PCIe-based drives are the fastest products available to consumers.

When considering all these parameters, it should be remembered that the specifications provided by the manufacturers are achievable under strictly defined conditions, so that different tests reflect different operating scenarios of the drives. Some drives are able to maintain a certain parameter for a longer period of time, while others will only reach a certain speed temporarily. More demanding users should compare the results of tests carried out in the same programs by comparing several drives with each other. 

Reliability and endurance of SSD 

Let’s now move on to reliability, which is particularly important for those who process large volumes of files or store important data. The durability of the drive, the most important factor for many users, is determined by the mysterious sounding parameters of TBW and MTBF and is directly related to the type of NAND flash component used. The most popular components used in SSDs at the moment are those manufactured in TLC (Triple-Level-Cell) and MLC (Multi-Level-Cell) technology. TLC components offer performance and reliability that should be sufficient for the average user. More demanding users who expect greater stability and comfort from their SSDs should focus on the MLC drives that offer greater performance and reliability.

Let’s now come back to the shortcuts: the Total Bytes Written (TBW) parameter determines the drive’s lifetime in gigabytes. The amount of data processed by users during the day varies greatly and may range from several hundred megabytes to several dozen gigabytes. The TBW parameter for TLC-based drives should be sufficient for the average user even long after the warranty period, which is typically 3-years, has expired. MLC-based drives have a TBW parameter that often exceeds the requirements of the average user. Their manufacturers will usually provide users with a 5-year warranty, while ensuring that the drive lasts much longer. When comparing the offers of individual manufacturers, it should also be noted that many of them also limit the warranty period by the TBW parameter. This means that the warranty will not be accepted if the user exceeds the amount of written data specified in the terms and conditions, even if the general warranty period has not expired.

The Mean Time Between Failures (MTBF) parameter, measured in hours, means “the average time between failures”. While the values expressed in this parameter should not be read literally, it will certainly help determine how long a drive should serve us without failure.