ondrej1024
Posts: 136
Joined: Thu Dec 05, 2013 3:09 pm
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eMMC flash memory reliability

Fri Oct 13, 2017 8:27 am

Are there any data out there that show how reliable the CMs eMMC flash memory chip is?

The CM3 mounts the Samsung KLM4G1FEPD flash chip but I couldn't find any useful information on the number of read/write operations before the flash gets corrupted. Does the integrated controller perform wear leveling? How does this chip perform compared to a microSD card?

Has anyone here run some stress test to check the durability of this chip?

For a product design this is quite important information but I can't seem to find it anywhere.

Ondrej
The Telegea.org project: https://www.telegea.org

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
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Joined: Sat Jul 30, 2011 7:41 pm

Re: eMMC flash memory reliability

Fri Oct 13, 2017 10:53 am

Flash suppliers are generally fairly reluctant to release information like this, since the data is so dependent on the use case. In fact they simply don't release it. Also, Raspberry Pi do change flash suppliers over time, so it will also vary in that way. One thing to say that is valid is that the reliability is MUCH higher than flash cards, since it uses MLC rather than TLC flash., which is an order of magnitude more robust. You can mitigate lifetime issues by reducing flash writes fairly easily.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
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ondrej1024
Posts: 136
Joined: Thu Dec 05, 2013 3:09 pm
Contact: Website

Re: eMMC flash memory reliability

Mon Oct 16, 2017 10:08 am

Thanks for the info. In fact I didn't know about MLC and TLC flash technologies. Now I googled them so I have learned something new ;)
There is also eMLC which is enterprise grade MLC. But how can we know for sure that eMMC really uses MLC (or maybe eMLC) and SD cards use TLC? Couldn't find any information about that.

Knowing the technology the memory chips are based on would give us some good indication of the durability. I found in interesting article which explains NAND flash technologies here. The following table show a summary:
flash-tech-comparison.png
flash-tech-comparison.png (28.09 KiB) Viewed 430 times

So MLC seems to support just about 2 times more read/read cycles during its lifespan than TLC flash.
The Telegea.org project: https://www.telegea.org

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