A bit more on SD and SSD...wear characteristics.

[The Natural Philosopher]

Doing the research reveals the true case about wear on flash memory
style devices and that is that substantially reads do *not* damage the
cells at all, at least no more than reading, say, DRAM. It is block
erases and writes that do and so, paradoxically, when used as a PROM,
probably wear levelling is entirely unnecessary. And if done
gratuitously may actually reduce lifetime. By 'gratuitously;, I mean
that it is done when there is no write operation in progress.
I cannot see any reason why one would shuffle blocks around *except* as
a result of a write operation, however.

There appears to be one aspect of read operations that *does* disturb
the data (read distrurbance), and that is that read operations can
minutely affect the state of physically adjacent but unread cells.
However this is generally at least an order of magnitude below write
damage, and is normally dealt with by error correction.

So smart SSDS with good wear levelling will *occasionally* rewrite read
only blocks, but this is in terms of hundreds of thousands of reads.

In my particular application the reads to reasonably static
configuration files will exceed 32 million per annum, or rather they
would *without disk caching*...

Now I am unaware as to how long Linux will regard a read only file that
is fully cached (my files are less than 1kBytes) as valid. I cannot
see *any* reason why re-reading file data that the operating systems
*knows* has not changed, would result in any actual 'physical' reads to
the SD card *at all*.

And in fact in my particular application one code and data is loaded,
even changing the configurations files should not result in a physical
read, as the disk cache itself used to do the writing will retain the
information.

I think the summary of all of this research is significant for PI users
running Linux in what may be generally classed as 'read often, write
seldom' accesses to an SD card, and that is that by far and away the
greatest protection the card has is the Linux disk buffering algorithm
itself, provided that constant reads do not exceed its capacity. In a
typical 24x7 applications there is no reason why, post boot, any SD
reads should happen *at all*, once the disk cache is full. It also shows
the absolutely vital role that '-noatime' plays in protecting read only
files that are read continuously from producing unwanted writes.

As far as writes go there will (nearly) always be a 1:1 correlation
eventually between writes to the linux file system and writes to the SD
card: The exception being data that us rewritten to the same disk file
cache before it gets flushed to physical storage.

So the general rule in utilising the SD card in the most effective
manner, is to reduce writes to a minimum by firstly mounting the card
-noatime, and secondly using RAM disks to do any logging that you can't
turn off, and for all operations where ephemeral data are being recorded
and read, but which do not need to survive a reboot. Then, having a
superfluity of RAM available for disk caching will reduce SD *reads* to
essentially zero. No matter how often the file system is accessed by the
application.

And in fact using iostat on my running application shows no (physical)
reads or writes *AT ALL*. As evinced by the rock steady light on the Pi
Zero.



--
"If you don’t read the news paper, you are un-informed. If you read the
news paper, you are mis-informed."

Mark Twain

[Jörg Lorenz]

Am 11.08.23 um 11:54 schrieb The Natural Philosopher:

What exactly is your question?

--
Manus manum lavat

[The Natural Philosopher]

My question is "Why did you think that a post has to be a question?"

This is information for Pi people using SD cards. Condensing a mornings
research into some general practical conclusions.

If you are not interested in it, just skip it.


--
There’s a mighty big difference between good, sound reasons and reasons
that sound good.

Burton Hillis (William Vaughn, American columnist)

[Jörg Lorenz]

Am 11.08.23 um 17:21 schrieb The Natural Philosopher:

Because the posting otherwise is unsoliceted spam?

> This is information for Pi people using SD cards. Condensing a mornings
> research into some general practical conclusions.
>
> If you are not interested in it, just skip it.

I'll ask when I am interested.

--
Alea iacta est

[Carlos E.R.]

Not correct.

As we are in a Linux group, you might remember that Linus posted his
first kernel here (on comp.os.minix) and it was not a question.

>
>> This is information for Pi people using SD cards. Condensing a mornings
>> research into some general practical conclusions.
>>
>> If you are not interested in it, just skip it.
>
> I'll ask when I am interested.
>

--

Cheers, Carlos.

[Rich]

In comp.os.linux.misc The Natural Philosopher <t...@invalid.invalid> wrote:
> On 11/08/2023 13:24, Jörg Lorenz wrote:
>> Am 11.08.23 um 11:54 schrieb The Natural Philosopher:

[snip long research summary]

>>>
>>> And in fact using iostat on my running application shows no (physical)
>>> reads or writes *AT ALL*. As evinced by the rock steady light on the Pi
>>> Zero.
>>
>> What exactly is your question?
>>
> My question is "Why did you think that a post has to be a question?"

Well, you were responded to by Jörg -- it has a mental defect where it
can't help but be a prime asshole. That mental defect earned it a
permanant position in my killfile. I only saw it's response because of
your response.

> This is information for Pi people using SD cards. Condensing a mornings
> research into some general practical conclusions.

And condensing a few hundred scattered individual articles in the two
groups into a single place for future reference. It was a useful
summary post, even if Jörg had an issue.

> If you are not interested in it, just skip it.

Indeed, some can't seem to 'get' that simple bit of logic into their
thick heads.

[The Natural Philosopher]

Oh? You think that unsolicited information about Linux and rasberry Pis
is spam, in linux and raspberry Pi newsgroups?
What on earth do you think that spam acrually IS?

>> This is information for Pi people using SD cards. Condensing a mornings
>> research into some general practical conclusions.
>>
>> If you are not interested in it, just skip it.
>
> I'll ask when I am interested.
>

Well, next time why not shut the fuck up when you are not.

You don't get to decide policy.

All you have is a keyboard and a killfile. It's very democratic. You can
only create your own safe space, you cant dictate it for anyone else


--
A lie can travel halfway around the world while the truth is putting on
its shoes.

[Jörg Lorenz]

Am 11.08.23 um 23:07 schrieb The Natural Philosopher:

> Oh? You think that unsolicited information about Linux and rasberry Pis
> is spam, in linux and raspberry Pi newsgroups?
> What on earth do you think that spam acrually IS?

Postings from anonymous Trolls with fake identities.

--
Alea iacta est

[Pancho]

When is an identity real, and when is it fake?

Surely it is only fake if it is pretending to be someone, or something,
it is not.

[Jörg Lorenz]

Am 12.08.23 um 02:10 schrieb Andreas Kohlbach:

> On Fri, 11 Aug 2023 20:11:43 +0200, Carlos E.R. wrote:
>>
>> On 2023-08-11 17:48, Jörg Lorenz wrote:
>>> Am 11.08.23 um 17:21 schrieb The Natural Philosopher:
>

> You all forgot how to trim postings? :-/

>
>>>>> What exactly is your question?
>>>>>
>>>> My question is "Why did you think that a post has to be a question?"
>>> Because the posting otherwise is unsoliceted spam?
>>
>> Not correct.
>>
>> As we are in a Linux group, you might remember that Linus posted his
>> first kernel here (on comp.os.minix) and it was not a question.
>

> Part was.

This is not comp.os.minix AFAIK. And who cares what happened 30 year ago
when we discuss the social compatibility of an identity?


--
Alea iacta est

[23k.304]

On 8/11/23 5:54 AM, The Natural Philosopher wrote:
> Doing the research reveals  the true case about wear on flash memory
> style devices and that is that substantially reads do *not* damage the
> cells at all, at least no more than reading, say, DRAM. It is block
> erases and writes that do and so, paradoxically, when used as a PROM,
> probably wear levelling is entirely unnecessary. And if done
> gratuitously may actually reduce lifetime. By 'gratuitously;, I mean
> that it is done when there is no write operation in progress.
> I cannot see any reason why one would shuffle blocks around *except* as
> a result of a write operation, however.
>
> There appears to be one aspect of read operations that *does* disturb
> the data (read distrurbance), and that is that read operations can
> minutely affect the state of physically adjacent  but unread cells.
> However this is generally at least an order of magnitude below write
> damage, and is normally dealt with by error correction.

This is substantially correct. Reading from an SD/SSD *can*
result in re-writes, thus shortening the life of the medium.
How MUCH/OFTEN ... well, it depends.

The BEST IDEA is to shift EVERY relevant file that
might possibly try to be read/writ to/from an SD off
into RAM as quickly as possible. Depending on your
distro you might be able to shift the entire OS to
RAM. Some "live" distros are kinda like this already.
A Pi with 4+ gb of RAM may be adequate enough for
this approach.

In any case, SDs are "smart" devices, they have a
controller to manage various needs. They are not
just "stupid" memory space even though they try
to *appear* as such to the user.

A few of my applications involve like a DECADE
of reliability. As such the hidden tricks of SDs
becomes relevant (as do memory leaks).

[Richard Kettlewell]

TNP’s been consistently posting under the same identity since, hmm, the
1990s I think? I think I’d call it a nom de plume.

At any rate, chatter about the longevity characteristics of storage
devices seems on topic here to me.

--
https://www.greenend.org.uk/rjk/

[The Natural Philosopher]

No-one could possibly be called Jörg Lorenz.


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

[The Natural Philosopher]

I have been using nyms since before the usenet was in the internet. Why?
Because I realised back in the 1980s that employers can peer into your
private discussions, and I didn't like it. I lost a job through not
being religious enough once.
What I have to say is what I have to say, regardless of whether it can
be connected to who I am as far as the electoral register, the bank and
the taxman are concerned.
There are some deeply weird and disturbed people on the internet as well
as elsewhere. I don't want my house set on fire or my tyres slashed any
more than already.
If you don't like it, just kill file me and STFU.

[The Natural Philosopher]

On 12/08/2023 08:43, Richard Kettlewell wrote:
> Pancho <Pancho...@Proton.Me> writes:
>> On 8/11/23 22:33, Jörg Lorenz wrote:
>>> Am 11.08.23 um 23:07 schrieb The Natural Philosopher:
>>>> Oh? You think that unsolicited information about Linux and rasberry
>>>> Pis is spam, in linux and raspberry Pi newsgroups? What on earth do
>>>> you think that spam acrually IS?
>>> Postings from anonymous Trolls with fake identities.
>>
>> When is an identity real, and when is it fake?
>>
>> Surely it is only fake if it is pretending to be someone, or
>> something, it is not.
>
> TNP’s been consistently posting under the same identity since, hmm, the
> 1990s I think? I think I’d call it a nom de plume.
>

It was earlier than that actually Richard. Before we met. It was pretty
much my 'social media' identity from the word go.

Curiously my experiences with Usenet absolutely put me off any
involvement with twitter or facebook.

> At any rate, chatter about the longevity characteristics of storage
> devices seems on topic here to me.
>

I think so, It was something I didn't know the full answer to, and
judging by the responses, the same was true of others. Everyone had a
bit of the picture, but the whole practical issue with respect to using
PIs was not available. I tried to summarise what everyone had
contributed into the salient issues.

--
"Women actually are capable of being far more than the feminists will
let them."

[Jörg Lorenz]

Am 12.08.23 um 09:43 schrieb Richard Kettlewell:

This is a general hardware question and not of any relevance to Linux in
particular.

--
Alea iacta est

[The Natural Philosopher]

On 12/08/2023 10:10, Jörg Lorenz wrote:
> Am 12.08.23 um 09:43 schrieb Richard Kettlewell:

>> At any rate, chatter about the longevity characteristics of storage
>> devices seems on topic here to me.
>
> This is a general hardware question and not of any relevance to Linux in
> particular.
>

If you look at the headers, assuming you can read, you will see that its
cross posted to comp.sys.raspberry-pi, and since all PIs other than the
Pico run off primarily an SD card, and primarily run Linux, it is of
extreme relevance to them.

It also touches on aspects of the Linux operating system - its logging,
and its file system behaviour, and its file cacheing, that are of
considerable interest to people who may not appreciate how deeply these
affect its performance.

Of course if you simply want to gaze at a glass terminal and pretend you
are back in the days of a PDP11, it's of no interest to you at all.

But don't judge everyone else by your own standards

--
Labour - a bunch of rich people convincing poor people to vote for rich
people by telling poor people that "other" rich people are the reason
they are poor.

Peter Thompson

[Ahem A Rivet's Shot]

On Sat, 12 Aug 2023 11:10:50 +0200
Jörg Lorenz <hugy...@gmx.ch> wrote:

> This is a general hardware question and not of any relevance to Linux in
> particular.

This group is about the Raspberry Pi range of SBCs almost all of
which use SD cards for primary storage and far from all of which run Linux.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
Host: Beautiful Theory meet Inconvenient Fact
Obit: Beautiful Theory died today of factual inconsistency

[Jörg Lorenz]

Am 12.08.23 um 11:48 schrieb Ahem A Rivet's Shot:

> On Sat, 12 Aug 2023 11:10:50 +0200
> Jörg Lorenz <hugy...@gmx.ch> wrote:
>
>> This is a general hardware question and not of any relevance to Linux in
>> particular.
>
> This group is about the Raspberry Pi range of SBCs almost all of
> which use SD cards for primary storage and far from all of which run Linux.

comp.os.linux.misc

Stop this X-posting! Get it?

--
Alea iacta est

[Jörg Lorenz]

Am 12.08.23 um 11:55 schrieb The Natural Philosopher:

> On 12/08/2023 10:10, Jörg Lorenz wrote:
>> Am 12.08.23 um 09:43 schrieb Richard Kettlewell:
>
>>> At any rate, chatter about the longevity characteristics of storage
>>> devices seems on topic here to me.
>>
>> This is a general hardware question and not of any relevance to Linux in
>> particular.
>>
> If you look at the headers, assuming you can read, you will see that its
> cross posted to comp.sys.raspberry-pi,

[Pancho]

Looking at previous postings, it seems about average "on topic" for
comp.os.linux.misc, it is 100% on topic for comp.sys.raspberry-pi.

I'm interested.

If you want to criticise, there is loads of other shit that we discuss
that isn't on topic.

[Jörg Lorenz]

Am 12.08.23 um 12:26 schrieb Pancho:

> Looking at previous postings, it seems about average "on topic" for
> comp.os.linux.misc, it is 100% on topic for comp.sys.raspberry-pi.
>
> I'm interested.
>
> If you want to criticise, there is loads of other shit that we discuss
> that isn't on topic.

Discussions with fake identities are futile.
The Natural Philosopher <t...@invalid.invalid>

--
Alea iacta est

[Jörg Lorenz]

Am 12.08.23 um 12:41 schrieb Jörg Lorenz:

Before and after Covid I have no intention to talk to masked and
anonymous people.

--
Alea iacta est

[Pancho]

Why are you talking to me?

[The Natural Philosopher]

On 12/08/2023 11:46, Jörg Lorenz wrote:

Well why don't you STFU then?
You have no way of knowing who here is using their real name, or even if
they have a real name. Many people have more than one name they commonly
use.

As for publishing a real email address, you must be bonkers. I have
enough spam as it is.

--
There is nothing a fleet of dispatchable nuclear power plants cannot do
that cannot be done worse and more expensively and with higher carbon
emissions and more adverse environmental impact by adding intermittent
renewable energy.

[Jörg Lorenz]

Am 12.08.23 um 12:48 schrieb Pancho:

Try to find out yourself.

--
Alea iacta est

[David W. Hodgins]

Trying to police a newsgroup that is not moderated will not work.

If you don't like the discussion filter it out of your feed, either by
poster, or by thread. Complaining will not stop it and just adds to the
noise, or gets your articles filtered out by others.

That's how usenet works.

Regards, Dave Hodgins

[Chris Schram]

On 2023-08-12, The Natural Philosopher <t...@invalid.invalid> wrote:
> On 12/08/2023 11:46, Jörg Lorenz wrote:
>> Am 12.08.23 um 12:41 schrieb Jörg Lorenz:
>>> Am 12.08.23 um 12:26 schrieb Pancho:
>>>> Looking at previous postings, it seems about average "on topic" for
>>>> comp.os.linux.misc, it is 100% on topic for comp.sys.raspberry-pi.
>>>>
>>>> I'm interested.
>>>>
>>>> If you want to criticise, there is loads of other shit that we discuss
>>>> that isn't on topic.
>>>
>>> Discussions with fake identities are futile.
>>> The Natural Philosopher <t...@invalid.invalid>
>>
>> Before and after Covid I have no intention to talk to masked and
>> anonymous people.
>>
>
> Well why don't you STFU then?
> You have no way of knowing who here is using their real name, or even if
> they have a real name. Many people have more than one name they commonly
> use.
>
> As for publishing a real email address, you must be bonkers. I have
> enough spam as it is.

Just to add a data point to this more and more ridiculous off-topic meta
discussion, for Usenet purpose only, email address in my From: header,
as well as in my .signature, is quite real and working. I cannot
remember the last time, if ever at all, I received spam email at that
address. Lucky? Maybe.

--
chri...@me.com is a filtered spam magnet. Email replies may be lost.
You're better off replying to this newsgroup.

[Carlos E.R.]

On 2023-08-12 11:55, The Natural Philosopher wrote:
> On 12/08/2023 10:10, Jörg Lorenz wrote:
>> Am 12.08.23 um 09:43 schrieb Richard Kettlewell:
>
>>> At any rate, chatter about the longevity characteristics of storage
>>> devices seems on topic here to me.
>>
>> This is a general hardware question and not of any relevance to Linux in
>> particular.
>>
> If you look at the headers, assuming you can read, you will see that its
> cross posted to comp.sys.raspberry-pi, and since all PIs other than the
> Pico run off primarily an SD card, and primarily run Linux, it is of
> extreme relevance to them.
>
> It also touches on aspects of the Linux operating system - its logging,
> and its file system behaviour, and its file cacheing, that are of
> considerable interest to people who may not appreciate how deeply these
> affect its performance.

Absolutely.

>
> Of course if you simply want to gaze at a glass terminal and pretend you
> are back in the days of a PDP11, it's of no interest to you at all.
>
> But don't judge everyone else by your own standards
>

--

Cheers, Carlos.

[The Natural Philosopher]

I don't feel it would be worth ones while.
--
It is the folly of too many to mistake the echo of a London coffee-house
for the voice of the kingdom.

Jonathan Swift

[Jörg Lorenz]

Am 12.08.23 um 13:23 schrieb David W. Hodgins:

> Trying to police a newsgroup that is not moderated will not work.

Sure. I made my point clear in the first answer to the OP.
But so many users thought they had to add something meaningful.

Case is closed for me now and the OP is (again) in my killfile. I will
always react to anonymous and impolite wisenheimers the way they deserve
in my opinion.

> If you don't like the discussion filter it out of your feed, either by
> poster, or by thread. Complaining will not stop it and just adds to the
> noise, or gets your articles filtered out by others.

What I observe since I participate in the usenet Anglosaxons often weigh
free speech higher than a minimum standard of decency and politeness
that helps to increase their credibility.

> That's how usenet works.

Believe me, after 22 years in the global usenet I know how it works.
Unmoderated Usenet is much more beneficial to all of us if the regulars
are very disciplined.

--
Alea iacta est

[Bobbie Sellers]

He wants to spread his ideas. Some are very bad ideas.
For example there was a Before Covid but there is no After
Covid. 300-400 US citizens are dying prematurely from
Covid each week. I started working on my 87th year yesterday
and wear filter masks in many situations because you do not
know what is in the air in crowds any longer.

Surprise the next Plague is here but it is the one
the Federal Government is treating as over.

And people wearing masks may not be anonymous but are
trying to protect others from their own infectious exhalations.

bliss - Dell E6540- PCLinux 2023.07- Linux 6.4.8- KDE/Plasma 5.27.7

--
bliss dash SF 4 ever at dslextreme dot com

[Rich]

In comp.os.linux.misc The Natural Philosopher <t...@invalid.invalid> wrote:
> On 11/08/2023 22:33, Jörg Lorenz wrote:
>> Am 11.08.23 um 23:07 schrieb The Natural Philosopher:
>>> Oh? You think that unsolicited information about Linux and
>>> rasberry Pis is spam, in linux and raspberry Pi newsgroups? What
>>> on earth do you think that spam acrually IS?
>>
>> Postings from anonymous Trolls with fake identities.
>>
> No-one could possibly be called Jörg Lorenz.

Jörg earned a permanent position in my kill file by being a complete
arsehole. This entire meta discussion indicates that the mentally
disturbed individual behind the nym remains just as much an arsehole
now as then.

Best to just killfile it and more along.

[The Natural Philosopher]

On 12/08/2023 15:29, Jörg Lorenz wrote:
> What I observe since I participate in the usenet Anglosaxons often weigh
> free speech higher than a minimum standard of decency and politeness
> that helps to increase their credibility.
>

What a pompous prick.

--
"A point of view can be a dangerous luxury when substituted for insight
and understanding".

Marshall McLuhan

[The Natural Philosopher]

One investigates to see if there is any sanity behind the mask. Then
moves on. There is none.

[Jörg Lorenz]

Am 12.08.23 um 16:51 schrieb Bobbie Sellers:

> He wants to spread his ideas. Some are very bad ideas. For example there
> was a Before Covid but there is no After Covid. 300-400 US citizens are
> dying prematurely from Covid each week.

Much less than from the pollution by cars.
Your opinion I do not share.

--
Alea iacta est

[MarioCCCP]

I completely disagree, since he, after a technical
discussion (to prove the conclusions), went on to give
useful advices specific to Linux, i.g. the one about
"noatime" mount option, and the stuff about logging on a ram
disk.
You seem to be polemising for misterious reasons


>

--
1) Resistere, resistere, resistere.
2) Se tutti pagano le tasse, le tasse le pagano tutti
MarioCCCP

[Computer Nerd Kev]

In comp.os.linux.misc 23k.304 <23k...@bfxw9.net> wrote:
> In any case, SDs are "smart" devices, they have a
> controller to manage various needs. They are not
> just "stupid" memory space even though they try
> to *appear* as such to the user.
>
> A few of my applications involve like a DECADE
> of reliability. As such the hidden tricks of SDs
> becomes relevant (as do memory leaks).

At the point where you _need_ something to work for a decade, it's
probably worth looking at industrial SD cards rather than
off-the-shelf ones. These are commonly characterised by using SLC
flash, which trades storage capacity for more write cycles.

NAND flash types:
https://www.kingston.com/en/blog/pc-performance/difference-between-slc-mlc-tlc-3d-nand

The datasheet for this SLC SD card describes the controller's
reliability features (including wear levelling):
https://docs.rs-online.com/29d1/0900766b815d5fe1.pdf
(pages 11 & 12)

Here's sales info from another industrial SD card manufacturer, who
elsewhere also advertise SD cards with an "advanced wear levelling
algorithm":
https://www.atpinc.com/blog/industrial-sd-cards-factors-requirements-to-consider

I'm not sure whether the industrial SD card controllers really do
much more for increasing longevity in a read-only application
though.

--
__ __
#_ < |\| |< _#

[The Natural Philosopher]

On 13/08/2023 01:40, Computer Nerd Kev wrote:

> At the point where you _need_ something to work for a decade, it's
> probably worth looking at industrial SD cards rather than
> off-the-shelf ones. These are commonly characterised by using SLC
> flash, which trades storage capacity for more write cycles.
>
> NAND flash types:
> https://www.kingston.com/en/blog/pc-performance/difference-between-slc-mlc-tlc-3d-nand
>
> The datasheet for this SLC SD card describes the controller's
> reliability features (including wear levelling):
> https://docs.rs-online.com/29d1/0900766b815d5fe1.pdf
> (pages 11 & 12)
>
> Here's sales info from another industrial SD card manufacturer, who
> elsewhere also advertise SD cards with an "advanced wear levelling
> algorithm":
> https://www.atpinc.com/blog/industrial-sd-cards-factors-requirements-to-consider
>
> I'm not sure whether the industrial SD card controllers really do
> much more for increasing longevity in a read-only application
> though.
>

Indeed. It does seem that with the price of computing power falling so
massively, there is little reason *not* to add wear levelling to SD
cards. Which ultimately renders them as reliable as any other NAND based
flash device.

My interest is, as always, to understand just enough to get the job
done, which in this case means I want about 10-15 years of reliable
operation on a 24x7 basis.

Having noted that in normal operation as far as I have built it, the
unit is not accessing its SD card AT ALL apart from a daily write to
some logs, I think that there I will stop.

There happens to be a sufficiency of RAM to regard the SD card
essentially as EAROM.

That will do nicely.

--
Climate Change: Socialism wearing a lab coat.

[Andy Burns]

The Natural Philosopher wrote:

> Doing the research reveals  the true case about wear on flash memory
> style devices and that is that substantially reads do *not* damage the
> cells at all, at least no more than reading, say, DRAM. It is block
> erases and writes that do a

Hence the primary metric for SSD longevity is TBW (terabytes written).

[24k.305]

On 8/12/23 8:40 PM, Computer Nerd Kev wrote:
> In comp.os.linux.misc 23k.304 <23k...@bfxw9.net> wrote:
>> In any case, SDs are "smart" devices, they have a
>> controller to manage various needs. They are not
>> just "stupid" memory space even though they try
>> to *appear* as such to the user.
>>
>> A few of my applications involve like a DECADE
>> of reliability. As such the hidden tricks of SDs
>> becomes relevant (as do memory leaks).
>
> At the point where you _need_ something to work for a decade, it's
> probably worth looking at industrial SD cards rather than
> off-the-shelf ones. These are commonly characterised by using SLC
> flash, which trades storage capacity for more write cycles.

Those are pretty good. However within a certain range
I still rec FRAM. It's REALLY good and you can get I2C
or SPI interface. Capacity, alas, is a bit limited. But,
if your app requires keeping track of peak figures,
current state and such ... things that ARE going to change
a fair bit but MUST be remembered between reboots .......
if you want a decade you don't use SD or on-chip flash.

> NAND flash types:
> https://www.kingston.com/en/blog/pc-performance/difference-between-slc-mlc-tlc-3d-nand
>
> The datasheet for this SLC SD card describes the controller's
> reliability features (including wear levelling):
> https://docs.rs-online.com/29d1/0900766b815d5fe1.pdf
> (pages 11 & 12)
>
> Here's sales info from another industrial SD card manufacturer, who
> elsewhere also advertise SD cards with an "advanced wear levelling
> algorithm":
> https://www.atpinc.com/blog/industrial-sd-cards-factors-requirements-to-consider
>
> I'm not sure whether the industrial SD card controllers really do
> much more for increasing longevity in a read-only application
> though.

Well, as mentioned, there may be "sneak" writes of
various kinds. Those who make distros for PIs and
such TRY to shift everything off into RAM but they
can MISS stuff, or discount "lesser" stresses on
SD. The focus of such distros is still aimed more
at "hobbyists" than "industrial" and they make
judgements accordingly.

[24k.305]

I wrote a multi-channel environmental monitor for "field"
use a few years ago. It took 12 samples per hour. Does not
sound like much, but it adds up. The device also HAD to
store a lot of high/low and random params which could
change every sample.

For that I chose I2C FRAM. No wait states, effectively
unlimited re-writes. Better than SD or on-chip EEPROM.

This is NOT a solution for jamming an entire OS into
unless it's DOS 2.x but you (and hopefully the distro
writers) do your best to shift all the OS stuff into
RAM and kinda hope for the best. The params in the FRAM
take care of reboots, save "the state".

[sc...@alfter.diespammersdie.us]

The horse is dead. Quit beating it. If you find a topic annoying, killfile
it. (You do know how to use your newsreader's killfile facility, right?)

FWIW, I find you more annoying than this topic, so...

** PLONK ***

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