Odroid U3 Slow USB HDD

[melwinek]

I my Odroid U3 i have very slow hdd transfer rate.
Hy hdd is connected via 5V powered USB HUB.

# hdparm -t /dev/sda1
/dev/sda1:
Timing buffered disk reads: 38 MB in 3.08 seconds = 12.34 MB/sec

# hdparm -t /dev/sda1
/dev/sda1:
Timing buffered disk reads: 48 MB in 3.01 seconds = 15.93 MB/sec

# hdparm -t /dev/sda1
/dev/sda1:
Timing buffered disk reads: 40 MB in 3.00 seconds = 13.31 MB/sec

In my desktop PC also via this HUB is 30 MB/sec

Why is it so slow?