Demand Based Hierarchical QoS Using Storage Resource Pools

The high degree of storage consolidation in modern virtualized datacenters requires flexible and efficient ways to allocate IO resources among virtual machines (VMs). Existing IO resource management techniques have two main deficiencies: (1) they are restricted in their ability to allocate resources across multiple hosts sharing a storage device, and (2) they do not permit the administrator to set allocations for a group of VMs that are providing a single service or belong to the same application. In this paper we present the design and implementation of a novel software system called Storage Resource Pools (SRP). SRP supports the logical grouping of related VMs into hierarchical pools. SRP allows reservations, limits and proportional shares, at both the VM and pool levels. Spare resources are allocated to VMs in the same pool in preference to other VMs. The VMs may be distributed across multiple physical hosts without consideration of their logical groupings. We have implemented a prototype of storage resource pools in the VMware ESX hypervisor. Our results demonstrate that SRP provides hierarchical performance isolation and sharing among groups of VMs running across multiple hosts, while maintaining high utilization of the storage device.