I'm sure this must be a FAQ but I can't find the answer on
beagleboard.org or searching elsewhere.
So, what's the maximum size microSD card one can use in a Beaglebone
Black? Plus are there any specific requirements for type, formatting,
etc.?
I run a BBB as a personal GIT server with a 128 GB Samsung uSD card.
Been up and running continuously for over two years. The only time it
has been off is when I stopped it, or the wall power failed.
I also run another BBB as a dedicated VPN server, with a 32 GB Samsung uSD card.
Same up-time comment.
— Graham
From memory it was:
Samsung 128GB up to 80MB/s EVO Class 10 Micro SDXC Card
I would guess from a memory address space limitation, Linux can address a larger memory space than you can afford to buy.
Just don’t bother with cheap “no name” uSD cards.
— Graham
From memory it was:
Samsung 128GB up to 80MB/s EVO Class 10 Micro SDXC Card
Thanks, that gives me lots of 'headroom' when compared with what I'm
actually likely to need/use.
I would guess from a memory address space limitation, Linux can address a
larger memory space than you can afford to buy.
Very true! I have systems with a few (three or four) terabytes of
rotating disks here at home but have no need for such things for my
BBB which is a data collection system on a small boat.
Just don't bother with cheap "no name" uSD cards.
SD cards (and USB sticks) seem to be plagued by fakes.
fyi: You'll need to be careful with SDXC. The am335x mmc/sdio
controller IP is only 100% rated for SDHC (max 32GB). (It doesn't
support the new SDXC voltages or all the new speeds...)
So stick with name brand "SDXC" microSD cards and test "1" before you buy many.
Likewise here, Samsung/Sandisk SDXC's seem to work fine.. 
Regards,
Thanks Robert, I don't even need anything like 32Gb, my 4Gb eMMC based
BBB (running Debian 7) is only half full still. Debian 9 won't need
much more space so I can still fit happily in 4Gb.
My question was more to find out what microSD cards I could use for
installing the new OS.
Plus I have two older BBBs with only 2Gb which is decidedly tight so
using a microSD card instead would provide more space so I can use
them as backup systems. Is there any difference in speed between eMMC
and microSD (though presumably SD cards vary in speed)?
Presumably one can remove /boot from the eMMC card and thus force
booting from the microSD.
Well the eMMC has a 8 bit interface (1), where as the microSD only has
an 4 bit interface (2)... However even generic microSD's can be
faster then the eMMC.. (kinda of a waste of the 8bit interface..)
Regards,