November 7, 2007: Seminar: Dr. Zahir Tari: "Dynamic Load Balancing for Systems Under Heavy Traffic and High Task Variation"

Seminar Announcement

Dynamic Load Balancing for Systems Under Heavy Traffic and High Task Variation

Dr. Zahir Tari
School of Computer Science and Information Technology, RMIT University, Melbourne, Australia
Friday, November 9, 2007
2:00 pm, Room SEO 1000


The most critical property exhibited by a heavy-tailed workload distribution is that a very small fraction of the very largest tasks make up a large fraction of the workload. This property makes the load very difficult to distribute using conventional task assignment policies (such as Random and LLF). Size-based task assignment policies (e.g. SITA-E, SITA-V, TAGS) have been proposed to handle heavy-tailed workloads, but suffer from limitations due to their static nature and assumption of prior knowledge of a task's service requirement.

In this talk I will be reviewing some of the work we did in the area of load balancing for servers under heaving traffic and high size variation. In our early work, we proposed LFF (Least Flow Time) approach that avoids to unbalance the load caused by very large tasks. LFF allocates tasks proportionally to the processing capability of participating servers by taking into account their remaining processing time. LFF-PRIORITY dynamically computes two priorities, namely task size and task size priorities, and put them in a priority based multi-section queue. Lately we proposed TAESR (Task Assignment based on Estimating the Service Requirement) as an extension of TAGS (Task Assignment by Guessing the Size). TAESR improves performance under heavy-tailed workloads by using multiple queues at each host, denoting restarted tasks as priority tasks and fast-tracking them to their final destination via priority queues. We found that TAESR performs significantly better (by a factor of three in some cases) than existing approaches under realistic conditions of high task size variation.

Brief Bio:

Zahir Tari is a full professor at RMIT University. He is the Director/ Leader of the DSN (Distributed Systems & Networking) discipline at the School of Computer Science & IT, RMIT (Australia). He acted as the program committee chair as well as general chair of several international conferences (e.g. DOA, CoopIS, ODBASE, GADA, IFIP DS 11.3 on Database Security). He is also the co-author of a few books. Dr Tari also published in several reputable journals (such as ACM/IEEE Transactions). More details about Zahir and his team can be found at

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