Delkin Blog

TBW, or terabytes written, is a function of multiple factors, but achieving a better TBW is an ongoing goal of many SSD developers. With the trend of 3D flash memory, which is anticipated to outpace 2D MLC storage, many users—particularly those whose flash memory drives store sensitive data—are worried about reliability. Is 3D flash less reliable than 2D flash, and how does 3D flash design impact TBW? Here is what you need to know about 2D vs 3D TBW to make an informed decision.

TBW Basics

TBW is calculated according to a simple equation. TBW=[(NAND Endurance) x (SSD Capacity) x (WLE)]/WAF. These individual factors are defined as follows:

• NAND endurance is the number of program and erase, or P/E, cycles which can be performed by a NAND flash device.
• SSD capacity is the total storage capacity of the entire SSD.
• WLE stands for wear leveling efficiency. WLE refers to the ratio of the average number of erases on all blocks to the maximum of amount of erases on any random block.
• WAF is write amplification factor. This a numerical value that represents the ratio between the amount of data a host’s flash controller writes and the amount of data an SSD needs to write. The closer a WAF is to 1, the better it is considered to be. Good WAF suggests higher endurance with a lower frequency of data written to flash memory.

TBW Reliability: 2D vs 3D

When comparing capacity, workload, and P/E cycles between 2D and 3D, the numbers are comparable between both kinds of flash. WAF is generally better on 2D flash, simply because the architecture of this kind of flash is ideal for lower write amplification. However, 3D flash is designed with an algorithm that improves its WAF performance. With the algorithm, WAF in 3D flash becomes comparable to that in 2D flash. In fact, the algorithm can lead to better TBW in 3D flash compared to 2D flash.

Delkin TBW Testing

Delkin understands the need to know TBW when selecting embedded memory. As such, we can work with you to calculate an estimated TBW based on the characteristics of a device. Alternatively, we can perform customized testing to obtain the actual TBW according to your specific workload and host.

Delkin specializes in customized testing for a variety of user needs in order to help each customer get the best possible performance from their devices. We will be happy to help you consider 2D vs 3D TBW and determine which option will be best for your application. To find out how we can help you meet your embedded storage needs, call us today.

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