Supported speed of sdcard? - Printable Version

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Supported speed of sdcard? - humanitypeace - 07-09-2018

I have a U3 rated micro-SD on which I have installed arch linux running on a Pine64+ 2GB model.

I have run a test and even though the card is rated to up to 95MB/s read speed and minimum rated write speed of 30MB/s I get constantly get read write rates of ranging only 10 to 15 MB/s (having done some testing with

dd if=/dev/mmblk0p2 of=/dev/null bs=2M count=1000 &

Is there any documentation which speed the mmc/sdcard is connected to the A64 of the Pine64+

Can those discouragingly slow speeds be confirmed, or is only my setup so sluggish.

PS: is there any alternative on the Pine64+ for a faster persistant memory storage (something like a emmc, sata, via GPIO bitbanging?)

RE: Supported speed of sdcard? - humanitypeace - 07-09-2018

It seems that allwinner chips interface to the sd-card is limited to either 16MB/s (in the sunxi-kernels) and
23MB/s max of 50Mhz 4bit bus on the mainline as stated at

To overcome the max 23MB/s  interface to the block device (the sd-card) of the Pine64, which I expect to have an impact on the overall performance as IO often seems the bottleneck, I have looked for alternatives

The Pine 64+ fastest interface seems to be Gigabit Internet, which yields a max about ~110 to 125MB/s. I have therefore run some tests wie nbd (network block device, see )

after loading the module 
modprobe nbd

and installing nbd-client userspace tool I can attach to a block device hosted on another computer via
ndb-client <ip-of-other-computer> <port> /dev/nbd0

Doing a performance test comparison we get
htparm -t /dev/mmcblk0
Timing buffered disk reads 34MB in 3.01 seconds = 11.31 MB/sec

htparm -t /dev/nbd0
Timing buffered disk reads 314MB in 3.00 seconds = 104.62 MB/sec

which I hope will improve performance somewhat.
Does anybody know if the ethernet in the A64 is parallel, separate (sort of DMA), or will network access eat CPU cycles?