SD cards are the literal worst.
they've expanded to be the size of small hard drives, and devices like the rpi keep using them as boot media, but they:
- use garbage tier low endurance flash cells internally
- have little to no overprovisioning for wear
- perform only the most basic wear levelling
- have no protocol level integrity checking
- have few internal error correction features, if any
- decay comparatively quickly without patrol scrubs
- do not perform patrol scrubs
- cannot do PLP
@kelpana @gsuberland USB-attached SATA or NVMe SSDs.
USB flash drives are the exact same (or often worse). Don't use them either.
@kelpana @gsuberland SD cards can be okay, if you use them read-only-only and buy from reputable vendors (e.g. Samsung).
If you really need R/W storage -- SPI NOR flash is a good option (together with proper wear leveling, etc.).
eMMC storage ICs are also available, often slightly more reliable and available from reputable vendors with a proper datasheet. They might work in some situations.
Otherwise, things get tricky...
No, NVMe won't work.
@raito @kelpana @gsuberland Yes, if you have a Linux kernel, you suddently have more good options.
"Microcontroller project" just didn't sound like Linux to me :)
@manawyrm @kelpana @gsuberland agreed; as we talked about RPIs in the start, I was considering the large spectrum of microcontroller projects
Nonetheless, I suppose that even ESP32 grade stuff could get access to a good implementation of something like UBIFS?
@raito @kelpana @gsuberland You can at least buy them from a proper source, with a datasheet and can be pretty much guaranteed to not get fake chips.
That helps a lot. Otherwise they're basically the same.
@gsuberland @raito @kelpana
Look at this datasheet: https://wmsc.lcsc.com/wmsc/upload/file/pdf/v2/lcsc/2007301503_Samsung-KLM8G1GETF-B041_C499918.pdf
You can also often configure/partition eMMC flash to work in pseudo SLC mode (trading size for reliability).
I know that at least some Micron eMMC has working built-in data refresh... Not sure about other vendors.
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