On a sunny day (Fri, 28 Feb 2020 00:15:36 -0000 (UTC)) it happened Martin
Gregorie  wrote in :

>On Thu, 27 Feb 2020 12:56:18 +0000, Jan Panteltje wrote:
>
>> For years I have followed the 3 methods backup system 1) SDcard FLASH 2)
>> normal harddisk (few TB is very cheap) magnetic 3) Blu-ray optical.
>> I stopped with optical for now as I have about 1000 DVDs and blue-rays
>> in a big alu lightproof box, mostly movies though, box is full!
>> Seems magnetic medium still wins.
>> Have not tried any SSD yet, not sure about the reliability of that
>> stuff,
>> price is high too.
>> Any practical experiences?
>>
>I don't trust Optical disks either: I've had several CDs written on PCs
>become unreadable after 3-4 years, so I no longer use them for storage: a
>CD RW is, after all only a dye layer that can be selectively changed by a
>bright light so, unlike a commercial, pressed and aluminised CD is
>guaranteed to deteriorate over time.

I think it is a bit like photograps, exposure time,
so light intensity * time.
I had DVDs go bad in a few hours that were kept in those transparent boxes on a
bookshelf
where part of the day the sun directly hits it.
From the light proof alu case 20 years old CDs I burned still work fine.

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