HDD vs. SSD

Comparison chart

HDD versus SSD comparison chart

	HDD	SSD
	current rating is 3.51/5 1 2 3 4 5 (316 ratings)	current rating is 4.21/5 1 2 3 4 5 (407 ratings)
Stands for	Hard Disk Drive	Solid State Drive
Speed	HDD has higher latency, longer read/write times, and supports fewer IOPs (input output operations per second) compared to SSD.	SSD has lower latency, faster read/writes, and supports more IOPs (input output operations per second) compared to HDD.
Heat, Electricity, Noise	Hard disk drives use more electricity to rotate the platters, generating heat and noise.	Since no such rotation is needed in solid state drives, they use less power and do not generate heat or noise.
Defragmentation	The performance of HDD drives worsens due to fragmentation; therefore, they need to be periodically defragmented.	SSD drive performance is not impacted by fragmentation. So defragmentation is not necessary.
Components	HDD contains moving parts - a motor-driven spindle that holds one or more flat circular disks (called platters) coated with a thin layer of magnetic material. Read-and-write heads are positioned on top of the disks; all this is encased in a metal cas	SSD has no moving parts; it is essentially a memory chip. It is interconnected, integrated circuits (ICs) with an interface connector. There are three basic components - controller, cache and capacitor.
Weight	HDDs are heavier than SSD drives.	SSD drives are lighter than HDD drives because they do not have the rotating disks, spindle and motor.
Dealing with vibration	The moving parts of HDDs make them susceptible to crashes and damage due to vibration.	SSD drives can withstand vibration up to 2000Hz, which is much more than HDD.

Components and Operation

A typical HDD consists of a spindle that holds one or more flat circular disks (called platters) onto which the data is recorded. The platters are made from a non-magnetic material and are coated with a thin layer of magnetic material. Read-and-write heads are positioned on top of the disks. The platters are spun at very high speeds with a motor. A typical hard drive has two electric motors, one to spin the disks and one to position the read/write head assembly. Data is written to a platter as it rotates past the read/write heads. The read-and-write head can detect and modify the magnetization of the material immediately under it.

In contrast, SSDs use microchips, and contain no moving parts. SSD components include a controller, which is an embedded processor that executes firmware-level software and is one of the most important factors of SSD performance; cache, where a directory of block placement and wear leveling data are also kept; and energy storage - a capacitor or batteries - so that data in the cache can be flushed to the drive when power is dropped. The primary storage component in an SSD has been DRAM volatile memory since they were first developed, but since 2009 it is more commonly NAND flash memory. The performance of the SSD can scale with the number of parallel NAND flash chips used in the device. A single NAND chip is relatively slow. When multiple NAND devices operate in parallel inside an SSD, the bandwidth scales, and the high latencies can be hidden, as long as enough outstanding operations are pending and the load is evenly distributed between devices.