Re: Move bookworm system from SSD to NVME

On 03/08/2024 12:52, Björn Lundin wrote:

On 2024-08-03 12:07, The Natural Philosopher wrote:
 

I am on the edge of my comfort patch here.
If I were building an SSD I would have a diode and a large capacitor inside it to make sure all its caches were dumped to NVRAM before the voltage collapsed completely.
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But on a big unit this could take a bit of time.
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What happens between a SATA/USB plug and the actual NVRAM is a bit of a mystery.
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We know its nothing like a 1:1 correlation between 'sector' and physical RAM location.
We knows that physical RAM locations are regularly shuffled for 'wear levelling'
When is all this done?
What happens if, during it, there is power failure?
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I honestly do not know, hence the warning to leave the SSD for a few seconds before yanking any power cords
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It can do no harm

 And that is my point. sync will do no harm either,
but it might save you, especially when you are dd()ing an image smaller that the RAM of the computer.
Like I have 32 Gb RAM, and dd an image of 4 Gb (like a headless) onto a SD-card to run an old pi. The interface is slow, yet dd reports done within a minute. sync takes a long time to flush it over.
 Just waiting a few secs will end in disappointment
 

Well I will be at some stage dd-ing about 60GByte across to a 2TB disk, but given the hassle, sync and a cup of coffee wait before unplugging it, is likely.
RK claims the wait afterwards isn't necessary.  Completing 'sync' is enough. He generally doesn't comment unless he knows.
I simply do not know how a command to something purporting to resemble a hard drive, that isnt can guarantee all data in it is flushed.
--
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