Modern technology has bought us a variety of storage technologies. Evolving from magnetic media to super-fast solid-state drives with no moving parts.
Flash media has become the staple for storage options everywhere from mobile phones, to portable computers, to enterprise servers.
But not all flash storage is the same, let's see the difference:
Flash storage works on the principle of holding data with transistors, and keeps the data on the transistor in a non-volatile manner by holding the charge floating.
Electricity flows from the source to the drain. When data to be written, current is also applied at the control gate. This causes the electrons to get trapped in the floating gate.
For erasing, the control gate potential is reversed.
These transistors are used in combination to store larger amounts of more useful data.
The common technologies used are nand flash, which uses a combination of transistors that form a nand gate and store data on it.
Typically, 1 bit of data is present in a single data cell, this is termed SLC, or Single Layer Cell. but many more bits can be there in a single cell as well, such as MLC or Multi-Layer Cell (2 bits per cell).
TLC which is Triple Layer Cell (3 bits per cell), and QLC which is Quad Layer Cell (4 bits per cell).
Each one of these has a cost, as well as speed and durability factors.
From SLC to QLC the cost reduces, but so does the write speed and the durability.
Flash storage being solid state technology, has no moving parts and has none of the issues associated with things such as mechanical failure.
Flash storage comes in a variety:
SD or Secure Digital is a proprietary technology that utilizes Flash memory in a compact standard package that communicates to the host via SDIO (Secure Digital Input Output).
SD cards are cheap and reliable for long term storage. their speed of communication is dependent on the specific communication revision they are based on.
In increasing order of speed there is SD-HC, SD-XC, SD-UC, and the fastest SD cards can almost reach 1 GB/s.
A lot of the speed and various parameters depend on the spec of the SD card's protocol, you can find more info about the parameters here.
SD card's best applications include photography storage, some Industrial applications which use them as ROM storage.
SD cards have relatively average durability for a flash storage medium, usually using TLC flash which can be the reason for their overall lower write speeds. Best used for long period storage which doesn't involve writing to it often.
Multi-Media Card is a technology that is widely used for media storage. As of today, the most common form factor of MMC is eMMC or embedded MMC.
eMMC is a standard maintained by the JEDEC association
It's more durable than SD, and is much faster in comparison.
However, since it is soldered to the motherboard of the device, eMMC cannot be replaced by end users.
It's used in a number of places such as smartphones, tablets, portable computers etc., Mostly applications range from portable device storage as it has better read and write endurance.
There have been many improvements and successors when it comes to a compact flash storage module, one of which is UFS (Universal Flash Storage) which comes with greater improvements too such as faster read and write speeds.
eMMC has the advantage of having an integrated controller that can do things such as wear leveling, to make sure that memory corruption doesn't become prevalent with constant writing.
This does make them more durable than SD cards, but they are still not as durable over the long run.
Solid state drives are the flash memory-based counterpart of spinning hard drives (or) HDDs, they are very power efficient, have very high storage density.
There are many types of SSDs, mostly differentiated by their protocol of communication,
The main protocols include:
SATA SSDs use the older protocol that hard disks used for communicating with the CPU.
Modern SSDs are fast enough to saturate the bandwidth offered by that protocol.
These SSDs have all the features offered by flash storage technology, like longer endurance and high storage density, and are slightly more expensive typical hard disks.
These primarily target replacing hard disk drives.
PCIe SSDs are part of the NVMe standard or (Non-Volatile Memory express), which uses high bandwidth PCIe lanes on your computer and is the fastest storage option when it comes to SSDs.
Modern PCIe SSDs use around 2x PCIe Lanes, but their speed can vary depending on the flash used and the controller bottlenecks.
Some PCIe SSDs use some extra DDR memory for caching, (the same kind your PC has) to offer a boost to speeds.
Another speed deciding factor can be the variant of PCIe generation. PCIe Gen 4 is the current fastest generation that is widely prevalent. However, the cost of the technology has it yet to be accessible to everyone.
As of now PCIe gen 3 SSDs are the sweet spot as of now when it comes to fast SSDs and reasonable cost.
SSDs overall have the best endurance when it comes to any type of storage medium, and are the fastest when it comes to reading and writing.
There are a lot of storage devices that use flash technology, for example USB flash drives.
These are the most popular portable version of flash media, Used for mass exchange of offline data.
These come with the same kind of flash technology as SSDs but in a small form factor, and communicate in a different way.
Similar to an SSD, these flash drives operate based on what version of USB they use such as a slower USB 2.0 flash drives vs a much faster USB 3.0 flash drive (which can almost be as fast as a SATA SSD).
Another common thing to note about both SSDs and USB flash drives since they use similar technology, is that the durability is proportional to their storage size, so a 16 GB flash drive has 2x the Durability compared to an 8 GB flash drive.
Different flash media have their applications in various places, from handheld electronics to powerful data centers and home computers.
eMMC and UFS power mobile smartphones, and small laptops. SSDs power most laptops these days. They also have started to become more popular in the datacenter space for high storage density, and Low power consumption.
For the daily user, you will most likely look into having SSDs for large local storage. If you need a large amount of storage prioritizing over speed, you might want to look into purchasing SATA based SSDs.
If you need a fast disk for your personal computer or desktop, an NVMe PCIe gen 3 SSDs should be suitable and provide the speed needed.
In total, flash media is a technology that has had a warm welcome and has changed computer technology for the better.
making computers faster, more power efficient, and has more improvements for years to come.