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When asking me for advice on purchasing a new computer or when having a PC Health Check done on your existing computers I often comment on the performance benefits of an SSD (solid state drive) rather than an HDD (hard disk drive).


This purpose of this FAQ is to explain in more details the differences between these drives.



Types of drive


The first image below shows you the most common types of drives found in home computers:


The two HDD (hard disk drives) are similar devices just different sizes, one designed for desktop computers and the other designed for laptop computers.


The other two are SSD (solid state drives) and there are several technical differences I won't go into here, but the first (2.5") is a direct replacement which connects using same cables/connections as the 2.5" HDD, whereas the NVMe SSD usually connects directly via a slot on the motherboard (main circuit board) in a computer.










Hard Disk Drive


A hard disk drive (HDD) is a mechanical device, which is probably best demonstrated in the video below where I have disassembled a drive so you can see the internal mechanism working.



In very basic terms the platters are where your data is stored and they spin round, the actuator moves the actuator arm and the head reads or writes data from the platter.


The speed the platter spins is determined by the specification of the drive, most desktop drives spin at 7200RPM (revolutions per minute) and most laptop drives at 5400RPM, this has a major affect on the performance of the computer, and on some computers you can actually hear the "thrashing" sound of the computer constantly reading from the hard disk which is why it is running so slowly.


When the computer is turned off the actuator arm is moved to the parking ramp away from the disk surface (platters) to protect it in case of an impact.  This is why with hard disk drives you need to be more careful when moving them about (or knocking / dropping them) if they are turned on, as if the platter is still spinning then the head could potentially impact it causing irreparable damage which would eventually result in data loss or disk failure.



Solid State Drive


Whereas a solid state drive (SSD) is made up completely of computer chips (see photo below), so there are no moving parts which means they are much faster and less prone to any damage from knocks or drops.






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