My friend Don writes
Slashdot is mostly devoid of useful info nowadays, but there were some useful comments about the value of CDs/DVDs/BlueRays in this article: https://hardware.slashdot.org/story/16/08/26/1420259/ask-slashdot-do-you-still-use-optical-media
He made for me this summary of important comments, which I am happy to share with you:
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I have collected almost a thousand audio CDs over the past 25 years. They served as masters for the digital copies I keep on my PC. Now I've discovered that a few of them are suffering from visible bit-rot, with the aluminum layer slowly being eaten / corroded in from the edge.
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I still use optical media to ensure clean install of various OS, because unlike USB, it is much harder to sneak one past checksum when you burn install DVD directly from ISO.
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Creating a bootable USB stick under Windows is a hit-and-miss affair. I just find it easier to pop in a blank disc, burn the Linux ISO to the disc, and boot off of that.
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CDs are cheap. Give some data to someone, don't care if you get the disc back.
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USB sticks have been effectively banned on DoD [department of defense] networks. We regularly use CD/DVD media to burn software and patches to then transfer it to the classified networks. The optical drives on the high side are almost always read-only to avoid issues with transport of classified off the servers.
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Unless someone starts producing USB flash drives [and hard drives] that have a hardware write protect switch that can't be countermanded by software, there is still a need for optical media. Otherwise there is no way to protect your data from being altered or deleted by bad actors. Cloud storage is about as 'volatile' as you can get; companies offering cloud storage could suddenly go out of business and screw you out of your data, or if they're being bad actors, futz with your data or delete it.
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Optical media is dirt cheap. SSDs/Flash memory is around 30 cents/GB. HDDs around 10 cents/GB. BD-Rs are around 2 cents/GB and if they follow the same pattern as CD-Rs and DVD-Rs, will eventually settle at around 0.8 cents/GB. [as of 2016]
Opinion of one reader:
CDs - Honestly, they're all pretty much the same now. If you really worry a lot about these, Taiyo Yuden makes high quality discs and Verbatim made ones that use AZO dye may have superior longevity. Maybe. By the time we know if they do or not, nobody will probably care. But honestly any name brand is almost identical in quality to Taiyo Yuden and Verbatim for CDs.
DVDs - You can buy Taiyo Yuden and you can buy Verbatim. Everything TY makes is great. Most of Verbatim's stuff is great except their cheap Life series of discs which is the same landfill grade crap that everybody else in the industry makes, including TDK. Note that Verbatim also makes DataLifePlus which is top notch and not the same at all as Life series. Skip everybody else here. And nobody knows if dual layer consumer burnable DVDs will last as long as single layer ones do.
BluRays - I pretty much stick to Verbatim (again, avoid Life series) and Panasonic here. Taiyo Yuden barely makes BD discs and last I checked they only made a single layer LTH type that some burners and some players may have problems with. LTH discs are a way to leverage existing DVD pressing plants so they can also make BD media and because these discs actually are written and read from backwards from normal BD media, some burners and some players have problems with them. Verbatim also makes some LTH BD discs and some regular BD discs. I advise avoiding the LTH media unless you are sure you can burn it and play it.