[Arm-netbook] Logging and journaling

[Julie Marchant]

On 02/08/2017 07:15 PM, Julie Marchant wrote:
> Mike, if that article is accurate, the study doesn't contradict what I
> said:
> 
>> None of the drives in the study came anywhere near their write limits,
>> even the 3,000 writes specified for the MLC drives

I wrote this while I was at work on my break, so now that I have more
time, let me elaborate.

Supposedly, in all cases tested, none of the SSDs were written to
anywhere near enough times to cause substantial wear. It is mentioned in
this article summarizing it that even 3,000 writes were not reached.
Most flash media can sustain at least tens of thousands of writes, so if
not even 3,000 writes were reached, it makes sense that none of the SSDs
tested failed.

However, it doesn't follow that this kind of wear is insignificant for
all flash memory. In particular:

* SSDs tend to be larger than SD cards, so they're not going to wear out
as fast unless the entirety of the space is being used and constantly
changed.
* The firmware of SSDs may be different from the firmware of SD cards.
For that matter, the firmware of SSDs may be different from the firmware
of other SSDs. Don't underestimate the power of wear leveling.

It still holds true that every change to any flash memory brings it
closer to the end of its life. It's just that other factors can do this,
too, and in some cases (e.g. SSDs) it may mean that the write cycle
limit is less important in practice.

-- 
Julie Marchant
https://onpon4.github.io

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