Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: The Natural Philosopher <tnp@invalid.invalid>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: Move bookworm system from SSD to NVME
Date: Sat, 3 Aug 2024 12:59:17 +0100
Organization: A little, after lunch
Lines: 48
Message-ID: <v8l62l$3d5il$18@dont-email.me>
References: <v8cqd6$1gdnp$1@dont-email.me> <v8e73l$1o2dm$1@dont-email.me>
 <v8frll$24ic1$1@dont-email.me> <v8ft4f$250uj$1@dont-email.me>
 <v8gamm$28554$1@dont-email.me>
 <20240801171000.46ce321a2dd0cb03be7cba00@eircom.net>
 <v8ghss$290sp$1@dont-email.me>
 <20240801192923.a827ba8d22853e9bc6c5cfb3@eircom.net>
 <v8gm3e$2atj2$1@dont-email.me> <v8go75$2bmb1$1@dont-email.me>
 <v8i9jp$2oohc$1@dont-email.me> <v8ikp3$2qqdd$2@dont-email.me>
 <v8ip08$2ralv$1@dont-email.me> <v8iph9$2rqib$2@dont-email.me>
 <v8jlc0$2ralv$2@dont-email.me> <v8kvgo$3d5il$4@dont-email.me>
 <v8l5m8$3easg$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Sat, 03 Aug 2024 13:59:18 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="f4b3c6a77b98e484ad341796ee5841fd";
	logging-data="3577429"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19fCdMZWpHqkW2uXSSV8F3kGu9gt4K2zQY="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:jITqtXPeZJIV3ojACv8jW0tHf4Q=
Content-Language: en-GB
In-Reply-To: <v8l5m8$3easg$1@dont-email.me>
Bytes: 3399

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.
>>
>> But on a big unit this could take a bit of time.
>>
>> What happens between a SATA/USB plug and the actual NVRAM is a bit of 
>> a mystery.
>>
>> 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?
>>
>> I honestly do not know, hence the warning to leave the SSD for a few 
>> seconds before yanking any power cords
>>
>> 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.


-- 
To ban Christmas, simply give turkeys the vote.