ADATA SP550 240GB SSD Review

TLC Vs MLC

TLC, MLC, SLC essentially are different types of NAND memory. All have different characteristics in terms performance, price and endurance.

SLC – Single level cell – High performance and Durability, but most expensive cost per bit.
MLC – Multi level cell – High performance and Durability, much lower cost as compared to SLC.
TLC – Tri level cell – Highest Density, Lowest cost per bit, Lower Durability.

In SLC NAND, a cell can be only in one of 2 states. This enables SSDs to have higher speeds and more durability, but at a very high cost. Then came in MLC, which was enabled a cell to hold more than one bit of information. This is probably done by having multiple states in the cell, which results in slower writes and lesser durability, but much lower cost per bit, as compared to SLC drives. TLC extends this to even more states (again, probably) and allowing for even higher density, but at cost of performance and durability.

So the lower endurance does sound a little scary, specially in the context of SSDs which are generally though of being fragile(though not always true). Adata is not alone though, samsung’s 850EVO (they started off with the 840EVO, industry’s first IIRC) as well as Crucial’s BX200 use TLC NAND. I hope memory manufacturers have improved this issue and is something we don’t need to worry about. Endurance is something that takes time to test and won’t be covered in this review. We will mainly be focusing on its performance and price position as of now and whether it is worth  have a TLC drive in the market.

If you guys want to know more, found some nice reads on different types of NANDs here:

http://www.anandtech.com/show/5067/understanding-tlc-nand
http://www.speedguide.net/faq/slc-mlc-or-tlc-nand-for-solid-state-drives-406
http://techreport.com/review/26523/the-ssd-endurance-experiment-casualties-on-the-way-to-a-petabyte/3
http://embedded-computing.com/news/nand-slc-mlc-tlc/

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