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Power loss and removing power
netPI does not have a physical reset button. The official method to shutdown the device is clicking "shutdown" within "Control Panel" management tile under the tab "System". The shutdown will take about 10 seconds and is finished when netPI's heartbeat LED "ACT" goes on for a second first and finally remains off forever. Only in this state it is allowed to remove netPI from its power source. This ensures there are no more write accesses to the SD card media that could else easily damage the file system when interrupted during an active write.

On the other hand, a power loss or an intended/unintended remove from power source cannot be controlled and can happen at any time still. netPI's industrial grade SD card supports a mechanism called Data Clone System (DCS) to prevent data corruption during active writes. DCS holds the data to be written in a second clone buffer always. On every power cycle the card checks the last written target block's data against the buffer. If different it re-writes it and solves the problem. This mechanism vastly reduce the risk of a damaged file system.
You never fail until you stop trying.“, Albert Einstein (1879 - 1955)

Dear Armin,

Would you please give me a favor?

I found the following explanation from Western Digital.

>Power Immunity for Reliability
>Advanced algorithms ensure data integrity in case of power loss, even if they occur during write operations

Is that the same function you mentioned about DCS above?

I am now asking Western Digital about the mechanism of power immunity for reliability because I want end-users to use netPI with confidence at unexpected power failure.
But Western Digital hasn't responded at all so far.

If you have some information on the mechanism in more details, would you please let me know?

Thank you very much for your information.
Best regards,
Hi Tad,

no I am not  a Western Digital specialist. I am just relying on what this company in writing.

I have one more document from Western Digital (fromer SANDISK company) appended to this post. Maybe this document includes more information for you.


Attached Files
.pdf   Western-Digital-SDSDQAF3-Industrial-microSD-Card-Data-Sheet-02-05-WW-02-00017-v6-0.pdf (Size: 933.46 KB / Downloads: 6)
You never fail until you stop trying.“, Albert Einstein (1879 - 1955)

I want to add one more thing to your question.

My post you are referencing is from year 2017. In year 2017 we didn't use the SD card from SANDISK/Western Digital as we are using it today. We used a card from company XMORE. And company XMORE called their mechanism DCS. So this is not the "name" SANSDISK/Western Digital is calling their own meachnism in my opinion. They are using a different name for sure.

Also I want to mention here that the main file system of netPI OS is ext4 which is a journaling file system. This file system tracks all write changes and is pretty is less prone to curruption but it is not immune 100% since there is a windows possible during power outages where an immediate write to the file jounal went wrong. Read on for more information about it on the Internet.
You never fail until you stop trying.“, Albert Einstein (1879 - 1955)


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