HDD (hard disk drive)
We can define a hard drive as a device that is used to store data. The hard disk internally has one or more platters which in turn rotate at high speed. It is there where one or more heads are usually located depending on the number of plates, where magnetic impulses are generated. These magnetic impulses represent the data, so these plates are magnetized and the information is -stored-. Subsequently, these heads are capable of interpreting this magnetism, being able to -read- the data as required. It can be considered a non-volatile memory.
It should be noted that the heads are suspended on the plates due to the great speed with which these plates rotate on a single axis driven by a motor. The capacities of today’s commercial hard drives span different capacities and prices, from 500Gb (giga-bytes) to more than 8TB (tera-bytes), where 1 GB represents 1024 Mb (megabytes) and 1 TB represents 1024 GB.
Solid state drive (SSD)
It is correct to say that a solid state drive has inside it an array of non-volatile memories that work for the purpose of storing data. The type of memories that are used are called flash memories , which are successors to EEPROM memories, which allow writing and reading in several directions simultaneously and by means of electrical impulses.
It is worth noting that flash memories have a higher operating speed when compared to those obtained through the use of EEPROM memories. Likewise, they have been used in more and more electronic devices, thanks to the storage capacity and speed that are achieved in an increasingly smaller size.
Currently the capacities of commercial solid disks cover different capacities and prices from 60 Gb to 960 Gb.
Differences between hard drive and SSD
|hdd hard drive||SSD Solid State Drive|
|In hard disks the operation is mainly mechanical.||In solid discs the operation is totally electric.|
|It has moving parts, like the platters and the head.||They have no moving parts.|
|They suffer wear with use.||They do not suffer from wear.|
|They are slower, because the head must move to -search- the data on the plate. (Average access time 12ms).||It is faster, because it works like a memory, where the data must only be -read- (Average access time 0.1 ms, about 120 times faster than a hard disk).|
|Transfer speeds are limited to an average of 100 to 200 MB per second depending on the hard drive||Transfer speeds are limited to an average of 300 to 1,500 MB per second depending on the SSD model and application.|
|Less efficient, because the moving parts have losses that translate into heat.||More efficient. The efficiency will be given by the consumption of the chips in Stand-by, generally much higher than that of a hard drive.|
|Less cost per Gb, which means you can buy a higher capacity hard drive for the same money as an SSD.||More cost per Gb, which means that you can buy a lower capacity hard drive for the same money as if it were an HDD.|