BPI-M3 using SSD on SATA-Port

Thx for the comprehensive answer!

Regarding SD cards it really depends on the card in question. While they can't exceed the 'usual' ~22 MB/s limitation regarding sequential transfer speeds there are huge differences regarding random I/O performance. Have a look at this thread here to see how even cheap SD cards with good controllers and high capacity are able to perform: http://forum.pine64.org/showthread.php?tid=469&page=2

You should also be aware that most of the times random I/O is more important than sequential transfer speeds (unless you record or stream video and stuff like that) so I would always have a look at these numbers first.

What puzzles me is the difference regarding random write speeds with small record sizes on your eMMC. It seems you have a different eMMC than me. Can you please compare these values with yours:

                 cid: 1501004d384731474303dc0db061506f 
                 csd: d02701320f5903fff6dbffef8e40400d 
                 rev: 6 
                date: 05/1997 
                name: M8G1GC 
                type: MMC 
preferred_erase_size: 524288 
          cache_ctrl: 0 
          cache_size: 65536 
               fwrev: 0x0 
               hwrev: 0x0 
               oemid: 0x0100 
enhanced_area_offset: 18446744073709551594 
              manfid: 0x000015 
              serial: 0xdc0db061 
          erase_size: 524288 
  enhanced_area_size: 4294967274

sysfs entry, can't remember the correct one but you find it quickly using

find /sys -name oemid