HDD vs. SSD

A hard disk drive (HDD) is an old-school storage device that uses mechanical platters and a moving read/write head to access data. 

A solid-state drive (SSD) is a newer, faster type of device that stores data on instantly-accessible memory chips.

Beware! The above image shows price comparison of a laptop with a HDD and another with an SSD. 😱

How they store?

HDDs: An enclosure contains a series of platters covered by a ferromagnetic coating. The direction of the magnetization represents the individual bits. Data is read and written by a head (similar to the way vinyl record albums work) that moves extremely fast from one area of the disk to another. Since all of these pieces are “mechanical,” the hard disk is the slowest component of any computer – and the most fragile.

SSD: These newer types of disks store information on flash memory, which consists of individual memory cells storing bits that are instantly accessible by the controller.

How they acess data?

Sequential read/write operations: Copying and moving huge files (such as movies) is where the difference is most apparent. On old-school HDDs, the copying process takes 30-150 MB per second (MB/s), where the same action takes about 500 MB/s on normal SSD, or even 3,000-3,500 MB/s on new NVME SSDs. In this example, copying a 20 GB movie is complete in less than 10 seconds with an SSD, while a hard disk would need at least two minutes.

Small “4K” read/write operations: Most of the time, when you run Windows (or MacOS), open programs, or browse the web, you’re actually opening and manipulating thousands of smaller files, which are stored in small blocks of data (usually sized at 4K). The faster your disk can read (and write) these 4K blocks, the faster and snappier your system seems. With HDDs, the speed ranges from 0.1 to 1.7 megabytes per second (MB/s). SSDs and NVME SSDs, however, operate at much faster speeds of 50-250 MB/s in 4K reads/writes.

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