Is there a way to configure bitcoind to be nicer about its harddrive bandwidth usage? I'm running bitcoind and its using literally 100% of my primary SDD's throughput. This is making my computer run very slowly in some cases (eg saving files is absurdly slow). Is there a way to configure it to only us maybe 95% of the available throughput at max so other stuff can get through? 

OS: Windows
I don't think there's any way to configure bitcoin to self-limit.

That said, Windows has an IO scheduler, which shares read/write bandwidth between processes. You can tell this IO scheduler to deprioritize a specific process. This isn't directly accessible from Task Manager or Process Explorer, but there are two third-party programs, called Process Lasso and Process Hacker which are capable of changing this.

(Source.)

(I think your problem is more likely to be a CPU bottleneck than IO, but you asked for this approach, and I assume you have a good reason.)