On 24/10/2019 08:07, R.Wieser wrote:
> Knute,
>
>> A 32GB card written to 1000 times is 32TB.  Write 1 million bytes per
>> second to the card, 24/7/365 is 31.536 trillion bytes.  So at a million
>> bytes per second the card will last a year.  At only a thousand bytes per
>> second the card will last a thousand years.
>
> Writes to CD cards are not done per byte, but per block (its not EEPROM, but
> Flash).
>
> If such a block is just a half a KByte (a single sectors worth) and assuming
> random access writes (a single byte per block) your "thousand years" drops
> back to just two ...
>
> Regards,
> Rudy Wieser
>
>
Hence wear levelling etc.

Flash NVRAM is really pretty shit technology.

But it is the best we have

 From Wiki

...flash memory has a finite number of program – erase cycles (typically
written as P/E cycles). Most commercially available flash products are
guaranteed to withstand around 100,000 P/E cycles before the wear begins
to deteriorate the integrity of the storage.[57] Micron Technology and
Sun Microsystems announced an SLC NAND flash memory chip rated for
1,000,000 P/E cycles on 17 December 2008.[58]

The guaranteed cycle count may apply only to block zero (as is the case
with TSOP NAND devices), or to all blocks (as in NOR). This effect is
mitigated in some chip firmware or file system drivers by counting the
writes and dynamically remapping blocks in order to spread write
operations between sectors; this technique is called wear leveling.
Another approach is to perform write verification and remapping to spare
sectors in case of write failure, a technique called bad block
management (BBM). For portable consumer devices, these wear out
management techniques typically extend the life of the flash memory
beyond the life of the device itself, and some data loss may be
acceptable in these applications. For high-reliability data storage,
however, it is not advisable to use flash memory that would have to go
through a large number of programming cycles. This limitation is
meaningless for 'read-only' applications such as thin clients and
routers, which are programmed only once or at most a few times during
their lifetimes..."

 From the above SSDS that always have wear levelling are now better than
SD cards that do not, but some SD cards now DO.


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Climate Change: Socialism wearing a lab coat.

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