Coupled placement in modern data centers

We introduce the coupled placement problem for modern data centers spanning placement of application computation and data among available server and storage resources. While the two have traditionally been addressed independently in data centers, two modern trends make it beneficial to consider them together in a coupled manner: (a) rise in virtualization technologies, which enable applications packaged as VMs to be run on any server in the data center with spare compute resources, and (b) rise in multi-purpose hardware devices in the data center which provide compute resources of varying capabilities at different proximities from the storage nodes. We present a novel framework called CPA for addressing such coupled placement of application data and computation in modern data centers. Based on two well-studied problems - Stable Marriage and Knapsacks - the CPA framework is simple, fast, versatile and automatically enables high throughput applications to be placed on nearby server and storage node pairs. While a theoretical proof of CPA's worst-case approximation guarantee remains an open question, we use extensive experimental analysis to evaluate CPA on large synthetic data centers comparing it to Linear Programming based methods and other traditional methods. Experiments show that CPA is consistently and surprisingly within 0 to 4% of the Linear Programming based optimal values for various data center topologies and workload patterns. At the same time it is one to two orders of magnitude faster than the LP based methods and is able to scale to much larger problem sizes. The fast running time of CPA makes it highly suitable for large data center environments where hundreds to thousands of server and storage nodes are common. LP based approaches are prohibitively slow in such environments. CPA is also suitable for fast interactive analysis during consolidation of such environments from physical to virtual resources.