Every organisation depends critically on reliable high-performance storage. Driven by the high costs of maintaining and managing multiple local storage systems, there is a trend towards virtualised multi-tier storage infrastructures. The main limitation of such centralised solutions is their inability to guarantee application-level Quality of Service (QoS) without extensive and ongoing human intervention. This intervention is necessary since delivered QoS can vary extensively both across and within storage tiers, and also depends on the access profile of the data.
This paper presents the first steps towards the concrete realisation of a self-managing virtualised storage system which automatically allocates and migrates data throughout its lifecycle guided by user-provided QoS hints. Specifically, we use the Logical Volume Manager (LVM) to create a virtualised multi-tier storage infrastructure with variable performance and reliability profiles. On to that, we place an enhanced (but backwards-compatible) Linux Extended 3 Filesystem which we call ext3ipods and which supports QoS metadata. We describe the kernel modifications necessary to quantify the QoS provided by a given data layout, thus enabling the subsequent development of intelligent data placement and migration algorithms.
Information from pubs.doc.ic.ac.uk/franciosi-towards-qos-storage.