I don't know what the -sta suffix means, aside from that it's a last name suffix (Hoekstra comes to mind, a last name which could be translated as corner-stra or angle-stra). It's not very common though and I can't think of any other -stra names. My first thought is that someone named Dijkstra historically constructed dikes, but then Hoekstra constructed... corners or angles?! Unless hoek had a different meaning in the middle ages, that can't be it.

Edit: https://nl.wikipedia.org/wiki/Dijkstra (English page does not contain the important part)

Apparently -stra comes from some germanic word meaning "owner". I suppose Hoekstra owned the corner house and Dijkstra the dike.

> The suffix "-stra" is, like "-ster", derived from the old Germanic "-sater", to be translated as a seater or resident.

-- https://nl.wikipedia.org/wiki/Dijkstra (through Google translate)