Thank you for the reply. 
All flags put together upped the speed to ~1.60MiB/s(890KiB/s). Is that
mebibyte per second notation? The speed is about 1 megabyte/s then. Guess I'll
have to wait, pity it can't go faster.

>It is by default optimized NOT to clobber remote servers, and therefore not
>suitable by default for localhost, or network stress test.
So it doesn't scale up to hdd write speeds, it's capped internally, yes? If
so, can you give theoretical limit when the program throttles? Can it go, say,
10MB/s? Is there an architectural limit after security limit flag? Have I
reached the ceiling with my megabyte per second speed?