What do SLC, MLC and TLC mean for SSDs?

In another article, we have already looked at the difference between HDD and SSD as well as the advantages and disadvantages. Now let's go into more detail and introduce different types of SSD.

More about the HDDs and SSDs

The terms SLC, MLC and TLC refer to the type of SSD memory. They indicate how many bits are written per memory cell on an SSD.

What do the abbreviations stand for?

SLC stands for "Single Level Cell". As the name suggests, an SLC cell stores exactly one bit. MLC stands for "Multi Level Cell" and means that more than one bit is stored per cell. This is usually two bits per cell, as TLC ("Triple Level Cell") has now also been developed, with three bits per memory cell.

Of these three types, single level cells have the highest read and write speed. They also require less power, are more durable, more robust and suitable for an extended temperature range. However,  they only have a relatively small memory and are comparatively expensive. Multi-level cell SSDs, on the other hand, have a higher storage density and can therefore store a considerably larger volume of data.

How does storage density affect wear?

MLC and TLC SSDs are often criticized for not being durable enough. Since more information is stored per cell, wear is higher than with SLCs. For comparison: While manufacturers often specify a service life of 100,000 write cycles for single level cells, triple level cells only last for 1,000 write operations. MLCs have around 5,000 to 10,000 cycles.
This sounds comparatively little, but is usually absolutely sufficient. Thanks to technologies such as wear leveling, almost nobody has to worry about the durability of their SSD these days.

What is wear leveling?

Wear leveling (literally: "wear compensation") is used to extend the service life of an SSD - a technology that is often integrated into SSDs. An algorithm is used to distribute the write operations so that all memory cells are written to equally often and the SSD wears out evenly.

This technique also distinguishes between dynamic and static wear leveling. The former only distributes dynamic data, i.e. data that changes when something is deleted and something else is saved. To prevent some cells from being written to only once while others are already failing, static wear leveling also moves static data to other blocks. The dynamic variant is often found in USB sticks, while static wear leveling is usually used for SSDs.

What kind of SSDs does spo-comm sell?

spo-comm offers Multi Level Cell SSDs in various sizes as standard, as these offer a high storage volume at a  suitable price-performance ratio. Some PCs (such as the WINDBOX or RUGGED series) can also be ordered with a 16 or 32 gigabyte SLC SSD. These are suitable for an extended temperature range of -40 to 85 degrees, but - despite the lower storage density -  are priced somewhat higher.