Current practice for acquiring computational resources

The study of the current practice has been conducted in collaboration with experts from the field of computational modelling. The modellers have access to a local HPC setup for running compute intensive jobs. They include a Professor (hereon referred to as Professor A) and a doctorate student (hereon referred to as Student B) working in the modelling group in University of Leeds.

3.2.1. Current practice: Introduction

The local HPC setup at the University of Leeds consisted of computing clusters and very large computing servers. The last chapter reported on the field of cluster computing (see section 2.6.2.1). People involved in the current practice include: computational modellers, laboratory managers and lab directors. Inputs from these experts are vital in pursuing this research; as they would outline the requirements and expectations for the envisioned system. A brief description about the people and their roles is given below.

 Computational Modeller

Position: Student A is a PhD student in a scientific computation group. Research Interests: Developing efficient, accurate and reliable computational techniques for the solution of partial differential equations. The majority of his research work has involved the Elasto Hydrodynamic

Lubrication (EHL) problems.

Priorities: Deriving results of interest to the wider scientific computing

community, for publication in papers and thesis. Develop modelling framework for EHL problems.

 Laboratory Manager

Position: Laboratory Manager C is a research assistant who is responsible

for managing access to the local HPC setup.

Research Interests: C is interested in supporting researchers performing

HPC simulations of fluid flow for EHL.

Priorities: Managing the service which entails managing the job queue and

recovering the service in case of a failure.

 Laboratory Director

Position: Professor B is the laboratory director for the scientific computing

group.

Research Interests: Professor B‟s general research area is Scientific

Computing specifically he is interested in efficient, accurate and reliable computational techniques for the solution of partial differential equations. The majority of his research work has involved with the development and analysis of computational algorithms using HPC systems.

Priorities: Acquiring funding for maintaining the local HPC setup.

Responsibilities also include keeping supervising the service managers.

3.2.2. Interviews with the experts

Semi-formal interviews and discussions were conducted with the computational modeller and the lab director. A selection of questions and answers from these interviews are as follows.

3.2.2.1. Computational modeller interview

The interview with the computational modeller was held on the 26th of August 2009 at the computing lab.

Question 1: Describe your need for HPC resources.

Answer: “The research experiments are performed iteratively where each

step involves generating a computational mesh and using it to run the experiment. The code for generating the mesh needs only minor changes for each run. The code for the actual experiment is written individually per iteration. Over the lifecycle; the size of the mesh varies between some hundred Mega Bytes (MB) to tens of Giga Bytes (GB). The local HPC resources are used for running the experiment while meshes can be generated on the local machine.”

Question 2: Describe the process of acquiring HPC resources.

Answer: “The process starts by lodging a request for required resources.

This is submitted to a job queue. The request includes information on the functional requirements and the time for which the resources are required. The functional requirements include memory, processing and storage these outline these identify the required resources. Requests that require more than twelve hours of time are catered only during the weekends.”

Question 3: Describe the advantages of using the current HPC setup.

Answer: “The research experiments would take days on a personal computer

while on a HPC machine these take hours. Therefore availability of large amounts of HPC resources is the main advantage.”

Question 4: Describe the disadvantages of the current HPC setup.

Answer: “The key issues faced by me in undertaking this work include

waiting for job execution as each job is submitted to the job queue. The wait is worse for jobs longer than 12 hours as these are catered only during the weekends. The other issue is, in regards to specifying the amount of time it takes the job to finish. It is very difficult to predict the precise time a job takes to finish and one can only predict probable times. If the prediction is incorrect and the job takes longer, it gets dropped and one has to start from scratch. Another issue is due to the fixed resource size; which means that there are no provisions for coping with surges in resource demand. At times of high demand the queues get longer which translates into more waiting time for each job.

3.2.2.2. Lab Director Interview

The interview with the computational modeller was held on the 3rd of September 2009 at his office.

Question 1: What are the benefits of the current HPC setup?

Answer: “The key benefit is in regards to the higher levels of trust and

security. As the physical resources are located and managed locally and access is only granted to authorized members, from within the research group.”

Question 2: What are the key issues affecting the current HPC setup?

Answer: “The main issue is in regards to cost; this high upfront costs of

buying the local HPC resources and maintenance costs for managing the resources. Another concern is redundancy as HPC resources become obsolete within a span of five years”

Question 3: What are your expectations from an envisaged system?

Answer: “There are a number of expectations from the envisioned system.

These include:

 Reduction in costs

 Multiple options for resource sizes

 Instant access to computational resources

 Ability to cope with surge in resource demand

 High levels of security and reliability ”

3.2.3. Current Practice Summary

In the current practice the computational modeller used HPC resources from the local HPC setup. In the current setup the modeller‟s progress was being hampered due to the delays in running long jobs as these were entertained only during the weekends. The modeller was also frustrated with the job request process which involved specifying the amount time for which the resources were required. As the time slots were booked in advance, jobs overrunning their time would be dropped which means rerunning the job. The lab director was most concerned about the reduction in costs; and the higher requirements for reliability and security.