Verifying SD Cards

On 04/05/2016 19:15, rickman wrote:
> On 5/4/2016 1:41 PM, Theo Markettos wrote:
>> In comp.sys.raspberry-pi rickman <gnuarm@gmail.com> wrote:
>>> I don't get why they keep increasing the size capabilities of the SD
>>> cards so incrementally.  SDHC only covered 4 GB to 32 GB expanding the
>>> size 16 fold.  SDXC expands the range another 64 fold.  Why so little?
>>> Memory capacity will continue to ramp up doubling every two years, so
>>> why not give the standard some legs?  SDXC will need to be replaced in
>>> another 8 to 10 years.

> I assume the SDHC cards topped out at 32 GB because they used FAT32
> which also tops out at 32 GB.  Rather than switch the format used, they
> just worked within that limit and postponed the bigger change for SDXC
> cards until later.

That was most likely the decision for that particular limit. The reason 
why there are incremental jumps between the formats is that SD Cards use 
serial addressing, and each card type uses a fixed number of bits for 
addressing giving a maximum storage size. The newer card types increase 
the number of bits to give more capacity, this would slow down access 
unless the bit clock was also increased, and that requires new reader 
hardware.

---druck

On 05/05/2016 02:35, Dennis Lee Bieber wrote:
> On Wed, 4 May 2016 18:44:24 -0400, rickman <gnuarm@gmail.com> declaimed the
> following:
>
>
>> Ok, how many are "small"?  Assuming each one wastes 16 kB, that's still
>> just 32 MB total.  Much less than 0.1% of a 32 GB SD card.
>
> 	Since 16kB is the cluster size for Windows on 32GB partitions...  NTFS
> is only 4kB per cluster up to multiple TB partitions.

NTFS isn't good for SD cards, its a journalled filing system meaning a 
lot more writes, and would work very inefficiently if data was 
continually flushed to the card, if it isn't flushed it would corrupt 
frequently if not properly unmounted before removal.

> 	But one may want to consider what the inherent SD card allocation unit
> is (and if you can get the format to align the clusters with allocation
> units).

As with any flash, the it is only possible to write in large blocks, 
this can be anything from 4K to 256MB, which is why there is such there 
is such a large difference in random write performance between different 
cards.

---druck

On Thu, 5 May 2016 14:12:04 +1000, Clifford Heath <no.spam@please.net>
Gave us:

>On 05/05/16 13:05, DecadentLinuxUserNumeroUno wrote:
>> On Thu, 5 May 2016 11:28:15 +1000, Clifford Heath <no.spam@please.net>
>> Gave us:
>>> On 05/05/16 11:45, mike wrote:
>>>> I think we had different math teachers...
>>>> 10e6 x 16 x 10e3 = 16 x 10e9 bytes
>>> I agree. We obviously had different math teachers.
>>> Hint: 10e6 is ten million. 10e3 is ten thousand.
>>> Clifford Heath.
>>    Bwuahahahaha!
>>    Mike is at least an order of magnitude dumber than everyone in Usenet
>> as well.
>
>I wouldn't know...
>
>But I do know that my IQ is a couple of dB lower on a bad day.
>
>Oops. Not allowed to use dB that way :)

  Think of it as a ratio of mental age over physical age.

On Wed, 04 May 2016 17:03:16 -0400, rickman wrote:

> On 5/4/2016 3:24 PM, mike wrote:
>> On 5/4/2016 11:46 AM, rickman wrote:
>>> On 5/4/2016 2:21 PM, rickman wrote:
>>>> On 5/4/2016 2:15 PM, rickman wrote:
>>>>>
>>>>> I assume the SDHC cards topped out at 32 GB because they used FAT32
>>>>> which also tops out at 32 GB.  Rather than switch the format used,
>>>>> they just worked within that limit and postponed the bigger change
>>>>> for SDXC cards until later.
>>>>
>>>> I'm a bit confused.  I just looked it up and FAT32 has an upper limit
>>>> of 2 TB!  So why can't FAT32 be used for one partition holding all of
>>>> a 64 or 128 GB SD card?
>>>
>>> I did a little digging and there is some sort of functional limit to
>>> FAT32 at 32 GB but it seems to mostly be Microsoft's laziness by not
>>> supporting the creation of larger partitions with their built in
>>> tools, or maybe just some of them.  I found a utility that let me
>>> format the 64 GB SDXC card to FAT32.
>>>
>>> So will I be able to boot a raspberry Pi from this SDXC card this way?
>>>
>>> http://arius.com/photos/FAT32_64GB.png
>>>
>> Isn't the FAT32 limit due to address space limitations?
>> If you want bigger partitions, you need to have bigger allocation
>> units.
>> Wastes a lot of space if you have many small files.
> 
> That's not a limit.  That's a tradeoff.  I suppose if you had millions
> of small files it would waste a lot of space.  Up to that point it's a
> macht nichts or mox nix, your choice.
> 
> The point is there is nothing to prevent the use of a single bootable
> partition on SDXC cards.
> 
> I really don't like partitioning mass storage into multiple smaller
> partitions.

Why Not?
it is a very good idea to keep your /home on a desperate partition.
also I would think with an SD card having a seperate data partition would 
help in the event of a partial failure.
using linux file systems is also preferred as FAT does not support Linux 
permissions

I would have the following partitions

/boot	fat32 - needs to be first partition
/	ext2 or ext4	(I like to avoid journaling on sd cards)
/home	ext2 or ext4

a swap partition seems to be unnecessary
-- 
I think we are in Rats' Alley where the dead men lost their bones.
		-- T.S. Eliot

Am 05.05.2016 um 08:47 schrieb druck:

> NTFS isn't good for SD cards, its a journalled filing system meaning a
> lot more writes, and would work very inefficiently if data was
> continually flushed to the card, if it isn't flushed it would corrupt
> frequently if not properly unmounted before removal.

I believe you've got the latter aspect backwards.  Journalling exists 
precisely to avoid that kind of corruption.  Non-journalling file 
systems like FAT corrupt a whole lot more easily and more thoroughly 
than journalling ones.

On Thu, 05 May 2016 12:17:34 GMT, alister <alister.ware@ntlworld.com>
Gave us:

>Why Not?
>it is a very good idea to keep your /home on a desperate partition.

  Desperate?

On 05/05/16 13:43, DecadentLinuxUserNumeroUno wrote:
> On Thu, 05 May 2016 12:17:34 GMT, alister <alister.ware@ntlworld.com>
> Gave us:
>
>> Why Not?
>> it is a very good idea to keep your /home on a desperate partition.
>
>    Desperate?
>
*extremely* desperate.

/home/dan

.....


-- 
"Anyone who believes that the laws of physics are mere social 
conventions is invited to try transgressing those conventions from the 
windows of my apartment. (I live on the twenty-first floor.) "

Alan Sokal

On Thu, 05 May 2016 13:45:33 +0100, The Natural Philosopher wrote:

> On 05/05/16 13:43, DecadentLinuxUserNumeroUno wrote:
>> On Thu, 05 May 2016 12:17:34 GMT, alister <alister.ware@ntlworld.com>
>> Gave us:
>>
>>> Why Not?
>>> it is a very good idea to keep your /home on a desperate partition.
>>
>>    Desperate?
>>
> *extremely* desperate.
> 
> /home/dan
> 
> .....

some typo's are better than others :-)



-- 
<knghtbrd> *sigh*  My todo list is like the fucking energizer bunny
<knghtbrd> It keeps growing and growing and growing and ...

rickman <gnuarm@gmail.com> wrote:
> On 5/4/2016 3:24 PM, mike wrote:
>> On 5/4/2016 11:46 AM, rickman wrote:
>>> On 5/4/2016 2:21 PM, rickman wrote:
>>>> On 5/4/2016 2:15 PM, rickman wrote:
>>>>>
>>>>> I assume the SDHC cards topped out at 32 GB because they used FAT32
>>>>> which also tops out at 32 GB.  Rather than switch the format used, they
>>>>> just worked within that limit and postponed the bigger change for SDXC
>>>>> cards until later.
>>>>
>>>> I'm a bit confused.  I just looked it up and FAT32 has an upper limit of
>>>> 2 TB!  So why can't FAT32 be used for one partition holding all of a 64
>>>> or 128 GB SD card?
>>>
>>> I did a little digging and there is some sort of functional limit to
>>> FAT32 at 32 GB but it seems to mostly be Microsoft's laziness by not
>>> supporting the creation of larger partitions with their built in tools,
>>> or maybe just some of them.  I found a utility that let me format the 64
>>> GB SDXC card to FAT32.
>>>
>>> So will I be able to boot a raspberry Pi from this SDXC card this way?
>>>
>>> http://arius.com/photos/FAT32_64GB.png
>>>
>> Isn't the FAT32 limit due to address space limitations?
>> If you want bigger partitions, you need to have bigger allocation units.
>> Wastes a lot of space if you have many small files.
>
> That's not a limit.  That's a tradeoff.  I suppose if you had millions 
> of small files it would waste a lot of space.  Up to that point it's a 
> macht nichts or mox nix, your choice.
>
> The point is there is nothing to prevent the use of a single bootable 
> partition on SDXC cards.
>
> I really don't like partitioning mass storage into multiple smaller 
> partitions.

Of course you use FAT32 only on cards/sticks/drives you want to use
for quick worry-free interchange of files.  The sneaker network.

Any use of those devices for permanent storage in a system should of
course use the native filesystem on that system or a filesystem
optimized for flash storage.

On 05/05/2016 13:30, Hans-Bernhard Br�ker wrote:
> Am 05.05.2016 um 08:47 schrieb druck:
>
>> NTFS isn't good for SD cards, its a journalled filing system meaning a
>> lot more writes, and would work very inefficiently if data was
>> continually flushed to the card, if it isn't flushed it would corrupt
>> frequently if not properly unmounted before removal.
>
> I believe you've got the latter aspect backwards.  Journalling exists
> precisely to avoid that kind of corruption.  Non-journalling file
> systems like FAT corrupt a whole lot more easily and more thoroughly
> than journalling ones.
>
No, NTFS only journals filing system meta data, so while it can 
automatically recover what looks like a valid filing system, the 
contents of the files may be corrupted.

This is actually a lot more insidious than with FAT where if it is 
corrupted the filing system is broken and it will usually tell you 
straight away, and you can restore from backup.

---druck