Le 19/01/2023 à 16:31, Rainer Weikusat via Dng a écrit :
> Didier Kryn<kryn@???> writes:
>> Le 18/01/2023 à 16:05, Rainer Weikusat via Dng a écrit :
>>> Lastly, I've recently read the manufacturer's (HP) disclaimer on the box
>>> of a USB stick. It's specifically disclaimed that data written to it can
>>> ever be read back again and users are remained that they should always
>>> have a backup on another medium.
>>     Beyond experience, have we an idea of what manufacturers disclaim
>> about spinning disks?
> The last two disks I bought didn't come with such a label. However, I
> didn't really look for one. If you know something specific, why not
> share it?
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    Quick web survey:

https://www.easeus.com/storage-media-recovery/ssd-vs-hdd-lifespan.html
claims 10 years for SSDs vs 3-5 years for HDD

https://www.ontrack.com/en-us/blog/hdds-vs-ssds is a more serious and
balanced discussion. In summary, HDDs are more sensitive to mechanical
hazard, thouth they feature shock protection mechanisms, but they are
most probably able to keep data for decades provided they are rarely
used and preserved from extreme temperature and from humidity. In other
words they are best for backup and archive.

https://tekie.com/blog/hardware/ssd-vs-hdd-speed-lifespan-and-reliability/
is also a detailed discussion and reaches the same conclusion: HDD best
for cold storage, SSD best for performance, but every write slightly
degrade the cells. SSDs definitely recommended for laptops and for
read-mostly.

https://www.tomshardware.com/features/ssd-vs-hdd-hard-drive-difference
gives numbers: an SSD can survive a shock of 1500g while  30g would
destroy an HDD. Other numbers: "SSDs are typically rated for around
200-600TB of writes before they are no longer covered by the vendor’s
warranty. HDDs are also rated sometimes at up to 150-300TB per year."

https://www.partitionwizard.com/clone-disk/is-ssd-good-for-long-term-storage.html
claims that SSDs lifespan is improving. The page provides a chart of
data lifespan vs temperature. lifespan increase with temperature when
the SSD is powered and inversely decrease with teperature when it is
disconnected. I don't find the numbers very encouraging: "If an SSD
commonly works at a temperature of 40 °C while staying in an environment
of 25 °C when power off, it is expected to last 105 weeks (about 2
years)." Surprisingly, their conclusion is " *Is SSD good for long term
data storage*? Yes!" I would say "Yes, if you keep the SSD in the
fridge." Why not? They also claim that the limited number of write
operations is not a problem for the daily use of a personal computer,
but it is for a data center.

    Beware: SSD loose their charge, therefore their data, when not
powered. The rate at which they loose the charge increases with
temperature; therefore, an SSD must be powered from time to time and
kept at a low temperature when not powered. This is to keep in mind for
archive/backup devices, and for the SD cards of the digital cameras, and
for USB memory sticks. HDDs used for archive/backup need only to be kept
at normal temperature in a dry atmosphere to avoid oxydation. Also,
avoid using SSD for memory swap.

--     Didier