thesis
Towards effective dynamic resource allocation for enterprise applications
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Abstract
The growing use of online services requires substantial supporting infrastructure.
The efficient deployment of applications relies on the cost effectiveness of
commercial hosting providers who deliver an agreed quality of service as governed
by a service level agreement for a fee. The priorities of the commercial
hosting provider are to maximise revenue, by delivering agreed service levels,
and minimise costs, through high resource utilisation.
In order to deliver high service levels and resource utilisation, it may be
necessary to reorganise resources during periods of high demand. This reorganisation
process may be manual or alternatively controlled by an autonomous
process governed by a dynamic resource allocation algorithm. Dynamic resource
allocation has been shown to improve service levels and utilisation and
hence, profitability.
In this thesis several facets of dynamic resource allocation are examined
to asses its suitability for the modern data centre. Firstly, three theoretically
derived policies are implemented as a middleware for a modern multi-tier Web
application and their performance is examined under a range of workloads in a
real world test bed.
The scalability of state-of-the art resource allocation policies are explored in
two dimensions, namely the number of applications and the quantity of servers
under control of the resources allocation policy. The results demonstrate that current policies presented in the literature demonstrate poor scalability in one
or both of these dimensions. A new policy is proposed which has significantly
improved scalability characteristics and the new policy is demonstrated at scale
through simulation.
The placement of applications in across a datacenter makes them susceptible
to failures in shared infrastructure. To address this issue an application
placement mechanism is developed to augment any dynamic resource allocation
policy. The results of this placement mechanism demonstrate a significant improvement
in the worst case when compared to a random allocation mechanism.
A model for the reallocation of resources in a dynamic resource allocation
system is also devised. The model demonstrates that the assumption of a constant
resource reallocation cost is invalid under both physical reallocation and
migration of virtualised resources