Frank Denneman, senior technical marketing architect within the Cloud Infrastructure Product Marketing group at VMware, recently wrote a blog post stating the resource management team at VMware is interested in your opinion about a feature in development; storage reservations.

He writes:

The current version of Storage I/O Control provides tools to prioritize and provide fairness to I/O streams of virtual machines. However the current version does not provide a function to specify number of IOPS to guarantee a minimum level.
Because the storage subsystem can be shared, external workloads can impact the performance capacity (in terms of IOPS) of the datastores and therefore a guarantee cannot be met temporarily. This is one of the challenges that must be taken into account when developing storage reservations and we must understand how stringent you want the guarantee to be.