Mark - I agree with your point that modern disk is cheap to purchase, which can reduce the value of HSM. However, many computer rooms are struggling with the heat and power issues of a lot of rack mount systems and hot-running disk. The escalating cost of energy and pressing problems of global warming really need to be considered. As in our case, HSM often used for storing a vast amount of static information (system logs, accounting files, installation packages, etc.) which seldom needs to be looked at. It makes more sense to exploit the HSM tie to existing tape library storage to hold such bulk on dormant, rather than active, media, with stub file representation in familiar directory structures (as opposed to TSM Archive storage, where "visibility" is inconvenient). So, we accept the warts of Unix HSM for the value it provides us.
Richard Sims