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=== Embedded Linux systems with eMMC or SD cards ===
Another typical use case refers to the eMMC's and SD cards. As explained [http://www.linux-mtd.infradead.org/doc/ubifs.html#L_raw_vs_ftl here], these components are FTL devices, where FTL stands for ''Flash Translation Layer''. This layer ''emulates a block device on top of flash hardware''. Therefore, these storage devices are used in tandem with file systems such as [https://en.wikipedia.org/wiki/Ext4 ext4] and [https://en.wikipedia.org/wiki/File_Allocation_Table#FAT32 FAT32]. Besides a raw NAND flash memory, eMMC's and SD cards integrate a microcontroller implementing the FTL and other important tasks as detailed in the rest of the document. The sections related to eMMC-based use cases are the result of a joint effort between [https://www.westerndigital.com/ Western Digital] (which purchased [https://en.wikipedia.org/wiki/SanDisk SanDisk] in 2016), Lauterbach Italy, and DAVE Embedded Systems.
==Wear-out==
LT = 20000 / 650 = 30.8 years
=====Experimental measurement of the '''actual''' written data=====
In many cases, WAF is unknown and can not be estimated either. As stated previously, the system integrator can determine the lifetime expectancy by adopting an experimental approach though. The following procedure describes how to determine the '''actual''' written data for the system used in this example.
