Thanks for providing coverage for the recently published research paper on PARDA (and for linking to my blog). I’m also writing a series of posts (http://virtualscoop.org/) explaining PARDA in easy to understand terms.

Like you said, one interesting question is whether to use “a common VM-oriented I/O scheduler that is seemingly independent of the back-end storage, or do I use array-based service controlling mechanisms that may be independent of the underlying VM technology platform?” One advantage the PARDA approach might have is the ability to provide per-VM level proportional sharing.

Irfan, VMware, Inc.
http://virtualscoop.org/