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=== Embedded Linux systems with eMMC or SD cards ===
Another typical use case refers to 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.
=== Example: embedded Linux system equipped with SanDisk SDINBDG4-8G-XI1 eMMC and ext4 file system ===
TBD
=== Example: embedded Linux system equipped with SanDisk SDINBDG4-8G-XI1 eMMC and ext4 file system ===
TBD
=== Example: embedded Linux system equipped with SanDisk SDINBDG4-8G-XI1 eMMC and ext4 file system ===
TBD
== Credits ==
This article was written in collaboration with:
Lauterbach Italy
Western Digital
U0002 moved page MISC-TN-017: Persistent storage and read/write file systems to MISC-TN-017: Persistent storage and read-write file systems without leaving a redirect: remove / from title (which is used in mediawiki for subpages
Therefore, before diving into these examples, we suggest to take a look at our [[Memory Tecnology Device (MTD)]] article where these subsystems are explained in more detail.
==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.
LF = (1GiB * 100k) / ((30k * 128KiB) * (365 / 1)) ~ 74 years
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==Power failures==
* [http://www.linux-mtd.infradead.org/doc/ubifs.html#L_writeback notes about UBIFS write-writeback support]
* [http://www.linux-mtd.infradead.org/doc/ubifs.html#L_writebuffer UBIFS write-buffer].
== Memory health monitoring ==
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