Quoting Arnt Karlsen (arnt@???):

> ..is/was these 2 separate swap spaces faster stand-alone than put
> together in a RAID0?

I'm not sure. Adding the additional complication of the md layer to
the Linux swapper thread's management of alternate access between two swap
partitions with equal priority seemed really unwise and _likely_ to
(at least) complicate operation, so I avoided doing so on the general
sentiment of simplicity.

In any event, I gather that there are tradeoffs.
https://unix.stackexchange.com/questions/15052/what-are-the-advantages-of-swap-on-a-raid-1-mirror-device
https://www.linuxjournal.com/article/5898