On the ECS appliance, ViPR Block is designed to provide general-purpose backend storage for customer deployed scale out application infrastructure.  Unlike in traditional enterprise block, ECS Appliance customers don’t typically need to optimize individual LUN performance on a workload by workload basis. Instead, they attach a series of LUNs with predictable performance to a number of hosts running the scale-out infrastructure.  Examples of these infrastructures include things like NoSQL stores (e.g., MongoDB, Cassandra, etc.), Graph databases, and home-grown scale-out applications.  Key use cases for ViPR Block on ECS appliance  are: Virtual Storage Infrastructure (VSI) enabling enterprises or service providers to deploy a multi-tenant ServerSAN via the ECS appliance for internal or external consumption.   The prototypical consuming application would be a Web-scale app with global endpoints (I.e., Next Gen, SaaS, Mobile, 3rd Platform, etc.). The direct consumer of ViPR Block on ECS appliance could either be those applications themselves, or they could be another layer of infrastructure (per the MongoDB and Casssandra references above).  Customers who want finer grained controls and greater performance flexibility beyond what ECS appliance provides can extend their environments using ViPR in conjunction with either specialized arrays, such as VNX, VMAX and XIO, or by using ViPR Block, powered by ScaleIO, in software form on top of their own hardware. In this deployment, ViPR Block use cases are OLTP and virtual storage infrastructure (VSI). 
What would I use ViPR Block for on an ECS Appliance? What applications? And how is the block capability on ECS Appliance different from what ScaleIO can deliver more generally?
ViPR Block vs. ScaleIO