A solid state drive (SSD) is a digital storage device much like the traditional Hard Disc Drive (HDD) with some key differences. SSD's are able to do many more input/output operations per second (IOPS) then HDD's which results in SSD's operating a lot faster then a HDD. Inside most SSD's are a drive controller, stacks of memory board micro chips and depending on the type of memory used, a battery. The controller, also known as a cache or a buffer is the "brains" of the SSD. The controller in a SSD is a central processing unit (CPU). The CPU is in effect a data traffic cop that directs data which will be "written" to the memory chips. For the written data to maintain it's status or state as data it needs an electrical charge to achieve a persistent state. In layman's terms, the data requires electrical power to continue to exist. SSD's achieve persistent data several different ways depending on the type of memory chip the data is being written to.
SSD's that use DRAM based memory are substantially faster than those that use NAND Flash memory. On the negative side DRAM memory is considered volatile memory and therefore requires a battery to maintain data to stay written when powered off. A popular workaround exists that helps bridge the gap between the limitations of both types of memory. The solution is to use DRAM to drive the CPU inside the drive controller but use NAND Flash memory as the place where the data is written. With this arrangement, only a small battery is required to power the DRAM. No battery is required for NAND memory therefore the SSD is able to be considered non-volitile.
Shantanu
How the data is stored
Most memory chips used today are NAND Flash Memory. The major reason for this is that NAND Flash memory is considered non-volitile memory which means that when it is powered off the memory will remain intact. Further, NAND Flash memory does not require a battery to keep the data written while the host device is powered off. The other popular type of memory used in SSD's today is called DRAM based.SSD's that use DRAM based memory are substantially faster than those that use NAND Flash memory. On the negative side DRAM memory is considered volatile memory and therefore requires a battery to maintain data to stay written when powered off. A popular workaround exists that helps bridge the gap between the limitations of both types of memory. The solution is to use DRAM to drive the CPU inside the drive controller but use NAND Flash memory as the place where the data is written. With this arrangement, only a small battery is required to power the DRAM. No battery is required for NAND memory therefore the SSD is able to be considered non-volitile.
Differences between SSD and HDD
How data is written
HDD's store data by magnetically writing data on a physical set of platters. HDD's are limited by physics in the sense that the platters and actuator arms can only spin and move to write on different platters at a finite speed. In comparison, SSD's store data on solid state computer chips which operate at the speed of light.SSD Vs. HDD: Advantages and Disadvantages
- Devoid of moving parts, the SSD is superior to HDD's in resilience to shock, vibration and extreme temperatures. SSD are used in mission critical situations like aeronautical, nautical, space and military applications where a devices failure rate, or chances that the device will work or not must be under a certain mean time between failures (MTB)
- In addition to speed, the absence of moving parts in SSD's results in lower power consumption compared to HDD. Lower Power consumption reduces the amount of heat emitted from the device which translates into less space required to dissipate heat. Less space used for heat dissipation means the SSD can have a smaller footprint then a HDD.
- Anecdotal evidence suggests a benefit in using SSD's in high end audio situations. Poor shielding surrounding HDD's can allow audio hu.
Shantanu
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