How common is it for sites to cluster TSM servers?

I'm looking for my next TSM position and have found at least one
situation, perhaps two, where the would-be client wants TSM
administrators who are familiar with CSM in an AIX/p-series
environment. As far as I can tell, that implies setting up the TSM
servers to fail-over so that if one fails, a hot-spare immediately
covers for it. I've never heard of this, and I've worked in a couple
of large, multi-TSM server environments.

My working theory is that someone took an AIX administrator set of
requirements as a template and didn't remove enough extraneous
buzzwords, but if more sites than I realize are clustering TSM
servers, I guess I should know that, too.

Thanks,
Nick