HDD is good or bad for logtime archival

[sonicmario]

HDD obtain many problems mechanical, magnetic, badblocks and errors, HDD not is good for longtime storage archival media? SSD, USB Flash Drive, microSD is better less fail?

[Arch Stanton]

Look up "NAND flash data retention".

[sonicmario]

I read many varies years retention flash: 5 years or 10 years or 20 years, HDD?

[Arch Stanton]

I read many varies years retention flash: 5 years or 10 years or 20 years, HDD?

Read more. Read about actual real world experiences.

Ask data recovery specialists and how they almost literally have to fight to read data from NAND flash chips.

These files are from a USB flash drive after it has been in a drawer for 2 years, 'safely' put away for storage:

Even if we assume that SSDs arguably use better NAND chips than USB flash drives or SD Cards, if left unpowered basically all NAND suffers from 'data bleed'. Modern NAND chips have even smaller margins than MLC, TLC NAND.

[sonicmario]

If powering use devices that use flash memory before 2 years will keep 100% of the data always?

I have a snes cartridge and it has the firmware saved inside a NOR flash

[Arch Stanton]

If powering use devices that use flash memory before 2 years will keep 100% of the data always?

You're looking for generic answers, I think there aren't other than that NAND based solid state drives are not ideal for long term cold storage.

How 'good' a NAND chip is depends on so many factors, starting with what type of NAND are we dealing with (SLC, MLC etc.)?

Then how did the manufacturer configure it, example how strong is error correction as this is a parameters that can be set. It's a policy decision. The weaker the error correction, the less retention errors it will be able to handle. You can verify/check using some cheap USB flash drive and use an MPtool, you can even disable error correction entirely.

Then how much erase cycles did the NAND endure: It's ability to retain data depends on number of program/erase cycles, gets worse the higher the wear.

Under what conditions was NAND programmed: Temperature at time of programming affects bit error rate. Intel goes even as far as simulating cosmic rays.

Anyway, there's tons of research and articles on the topic (circumstances and factors that influence data retention of NAND and whatnot). Arguably some research tests under unrealistic/theoretical circumstances but some times you have to in order to be able to measure effects.

[sonicmario]

when the media is used to store data it is not constantly erased and rewritten, this is the case with the firmware inside the NOR flash

Would you trust HDD or flash more for long term storage?

[pclab]

HDD Always!

[sonicmario]

What is the best HDD brand in terms of durability and resistance?

[pclab]

They all fail, that's why you need a backup!