SD card programing -

Robert Moskowitz rgm at htt-consult.com
Thu Apr 30 14:08:05 UTC 2015



On 04/30/2015 09:08 AM, Dave Ihnat wrote:
> On Wed, Apr 29, 2015 at 10:46:38PM -0400, Robert Moskowitz wrote:
>> I have a Microcomputer center a couple miles away, and they have mSD
>> cards by the dozens at the checkout counters.  Each comes with the
>> SD adapter.  I think I just spent $9 each for a few more 16Gb cards
>> for my testing.
> I've been using the EMTec cards carried by MicroCenter.  I don't trust
> no-name or store-branded cards.  There are just too many fraudulent cards
> out there.  I've considered using MicroCenter's, just because I can go back
> to the store if there are problems, but the difference in price hasn't been
> worth it.

That is why I blow away their partitions and do my own, even if I want a 
DOS partition.  I once, REALLY, got a USB stick from ecost.com that had 
this strange hidden partition on it with this interesting code that had 
an IP address imbedded in it.

> Also, another thing you should consider is that there are speed classes of SD
> cards from 3-10.  You want Class 10--10MB/s.  You'll often see Class 2,4,
> and 6 cards at great prices--there's a reason.

I am looking at the card I got last week and it says C10.

> I hate to recommend a Microsoft-based solution--try running it under
> wine or something, if it offends the sensibilities--but look for, get
> and run a little ditty called h2testw.exe (best site would be the source,
> http://www.heise.de/download/h2testw.html--it's a German author and site,
> but you can figure it out.)  There are Linux alternatives--the one that
> comes to mind is F3:
>
>    http://oss.digirati.com.br/f3/
>
> Others, and some discussion of the problem:
>
>    https://www.raymond.cc/blog/test-and-detect-fake-or-counterfeit-usb-flash-drives-bought-from-ebay-with-h2testw/
>
> Some think that a RPi OS running off a SD card should be "tuned"; others
> dismiss this, as the card specs give a large number of R/W ops before MTBF.
> Nevertheless, especially if you're going to run 24x7, some things just
> make sense:
>
>    o Turn on noatime in fstab
>    o Use tmpfs in fstab
>    o Use a bigger card--not for storage space, but wear leveling.

The latest uboot for F22 (and kernel) can just have uboot on the SD card 
and then switch to your sata for everything else.  That is the nice 
thing about Cubies (and Wands and a few others).  Real sata port.  Hans 
is working on USB drive support out of uboot, but I have not heard if he 
has that working yet.  There are a few things that won't made F22 and we 
will have to wait for F23 for them.

> As far as size--Raspbian comes as a 2GB image, which you expand to use the
> capacity of the card.  If you'r not going to do a lot of local data
> storage, 8GB will work well (and be a lot cheaper).  16GB is a nice
> compromise on cost/capacity (and wear leveling, if you believe in that as
> an issue).  32GB is pricy, and if you're thinking about that much storage
> maybe you want to hang a USB HDD or even SDD off the box; after all, we now
> have four USB ports with the Pi 2.

Better to go with a smallish SD and put on a USB drive for your root and 
such.



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