In this blog post, we’ll examine the data storage methods and performance differences between HDDs and SSDs using scenes from the movie ‘Password’, and explore how these differences between the two storage devices might play out in real-world situations.
In the movie ‘Password’, Milo, a promising Stanford University graduate, joins the software company NURV after receiving an offer from millionaire Gary Winston. When his closest friend, Teddy, is murdered, Milo notices something suspicious about Gary’s behavior and decides to infiltrate the company in the early hours of the morning to find Teddy’s killer. He then goes to the security office to review CCTV footage in an attempt to secure decisive evidence, but unfortunately, he fails to obtain the crucial evidence by a matter of seconds. So, if the security office computer had used an SSD (solid-state drive) instead of an HDD (hard disk drive) to store the CCTV data, could the outcome have been different? The movie ‘Password’, released in 2001, centers on the protagonists Milo, Teddy, and Gary Winston, as well as Synapse, NURV’s communication system.
Hard disk drives (hereinafter HDD) and solid-state drives (hereinafter SSD) are both storage devices used to store computer data. The data we need when working on a computer—such as the operating system, programs, documents, and photos—is recorded on these storage devices. However, HDDs and SSDs differ fundamentally in how they store and retrieve data. Generally, SSDs offer much lower latency and higher data processing performance than HDDs. In particular, while HDDs require physical movement of platters and heads to read and write data, SSDs electronically control NAND flash memory, eliminating the need for such mechanical movement. This structural difference is one of the most important reasons why SSDs operate faster than HDDs.
The data storage method of an HDD can essentially be compared to an LP record on a phonograph. You’ve probably seen how a phonograph record is played at least once in a movie or on television. In atmospheric films, a phonograph plays music by having a needle read the grooves on a rotating record. HDDs read and store data using a similar principle. However, instead of a phonograph record, an HDD uses a circular disk called a “platter” and a “head,” which corresponds to the phonograph’s needle. The head reads and writes magnetic information recorded on the surface of the platter. Magnetic information may sound unfamiliar, but it’s easy to understand if you think back to the magnets with north and south poles you played with as a child. In an HDD, data is stored by detecting and altering the magnetic state recorded in very small areas on the surface of the platter. Because the head must move quickly across the rotating platter to store or retrieve data, physical movement occurs. In other words, the operation of an HDD involves mechanical processes.
However, since SSDs use a completely different data storage method than HDDs, they do not require mechanical movement such as that of platters or heads. SSDs do not have the platters and heads found in HDDs; instead, they use semiconductor memory called NAND flash. Understanding NAND flash from an engineering perspective can be somewhat difficult, but it becomes easier to grasp if you think of it as an apartment complex. If you look at an apartment building on a dark night, you’ll see that some apartments have their lights on, while others have theirs off. You can think of NAND flash as a nanometer-scale collection of such apartments. However, actual NAND flash doesn’t simply store two states—on and off—but can store multiple bits in a single cell, depending on the cell type. SLC can store 1 bit per cell, MLC 2 bits, TLC 3 bits, and QLC 4 bits, and it records data by distinguishing between various charge states. Therefore, the analogy of “a lit apartment representing a 1 and an unlit one representing a 0” can be viewed as a simplified explanation for understanding the basic concept of NAND flash.
SSDs use multiple NAND flash memory chips and employ a controller to manage data efficiently. The controller manages the process of writing and reading data received from the computer to and from the NAND flash; it plays a central role in the SSD by tracking data locations, correcting errors, and managing memory usage. Depending on the product, SSDs may use memory such as DRAM or employ structures—like an SLC cache—to enhance write performance. Just as a car travels quickly along a multi-lane highway, an SSD efficiently processes data by utilizing multiple NAND flash channels. The cache can be understood as temporary storage used while data is being written to the NAND flash. However, not all SSDs use cache memory in the same way; depending on the product, some employ a DRAM-less architecture. The key point is that, during data processing, an SSD electronically controls the NAND flash rather than moving mechanical parts.
The absence of mechanical movement is one of the main reasons SSDs can operate faster than HDDs. To illustrate this with a relevant example, let’s think of “storage” as the process of returning books that people have borrowed from a library back to the shelves. In this analogy, an HDD—which requires mechanical movement—can be likened to a librarian physically walking to the shelf to put the book away. Conversely, an SSD—which requires no mechanical movement—can be likened to quickly and electronically transferring the book to its desired location. With HDDs, the read head must move to locate a specific position on the platter, resulting in physical seek time during the process of requesting and reading data. In contrast, SSDs do not require this seek process and therefore exhibit low latency, particularly when reading and writing small files from multiple locations. In the past, it was often stated that SSDs were about three times faster than HDDs, but this generalization is no longer accurate given the wide variety of SSDs and HDDs available today. Actual performance varies significantly depending on the interface and product; while SATA SSDs offer sequential transfer speeds several times faster than typical HDDs, PCIe-based NVMe SSDs can achieve transfer speeds of over several gigabytes per second in the latest generation of products. Additionally, SSDs have the advantage of producing very little operational noise since they lack mechanical heads and platters.
In the movie ‘Password’, Milo, who was trying to secure CCTV evidence to solve the mystery surrounding the death of his closest friend, Teddy, unfortunately fails at the crucial moment. However, if he had used an SSD instead of a hard disk drive, which requires mechanical movement, it’s possible that the nature of the storage device would have helped reduce the latency incurred during data read and write operations. That said, we cannot definitively conclude that using an SSD would have allowed him to overcome those few seconds and secure the evidence in the situation depicted in the movie. This is because a computer’s actual processing speed is influenced by various factors, including not only the storage device but also the CPU, memory, operating system, network, and the structure of the CCTV system. Nevertheless, if you feel your computer is slow, using an SSD instead of an HDD remains one of the most effective ways to improve its perceived performance even today. Even if you don’t face a life-or-death situation like Milo’s in the movie, it’s clear that the choice of storage device can significantly change your computer experience.
