Delay versus Stickiness Violation Trade-offs for Load Balancing in Large-Scale Data Centers

Most load balancing techniques implemented in current data centers tend to rely on a mapping from packets to server IP addresses through a hash value calculated from the flow five-tuple. The hash calculation allows extremely fast packet forwarding and provides flow `stickiness', meaning that all packets belonging to the same flow get dispatched to the same server. Unfortunately, such static hashing may not yield an optimal degree of load balancing, e.g., due to variations in server processing speeds or traffic patterns. On the other hand, dynamic schemes, such as the Join-the-Shortest-Queue (JSQ) scheme, provide a natural way to mitigate load imbalances, but at the expense of stickiness violation. In the present paper we examine the fundamental trade-off between stickiness violation and packet-level latency performance in large-scale data centers. We establish that stringent flow stickiness carries a significant performance penalty in terms of packet-level delay. Moreover, relaxing the stickiness requirement by a minuscule amount is highly effective in clipping the tail of the latency distribution. We further propose a bin-based load balancing scheme that achieves a good balance among scalability, stickiness violation and packet-level delay performance. Extensive simulation experiments corroborate the analytical results and validate the effectiveness of the bin-based load balancing scheme

The stickiness curves of dairy powder : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Bioprocess Engineering at Massey University

Powder stickiness problems encountered during spray drying are important to the dairy industry. Instantaneous stickiness is a surface phenomena that is caused by exceeding the glass transition temperature of the amorphous sugar in the powder, usually lactose in dairy powders. Instantaneous stickiness occurs at a certain temperature above the Tg of amorphous lactose and has been denoted as the critical "X" value. Whether powder particles are sticky or not depends on whether there is enough liquid flow on the surface between the particles. Two particles stick to each other when there is enough liquid flow to form a bridge between them after the contact. This project aimed to measure the instantaneous sticky point conditions for various dairy powders and to relate these to the operating conditions to give a commerical outcome for the dairy industry. The particle-gun rig was developed to simulate the conditions in the spray drier and the ducting pipe and cyclone. The stickiness of powder particles occurs after a short resident time in the particle-gun. Thus, stickiness is a surface phenomenon and the point of adhesion is the instantaneous sticky point. The amount of deposit on the plate was measured at a temperature, with increasing relative humidity. At a particular temperature and relative humidity, the powder stuck to the stainless steel plate instantaneously. This was observed by a sudden change in % deposition on a % deposition verse RH plot. The T-Tg plot and stickiness curve profile were developed to determine the critical "X" value for the dairy powders. The critical 'X' value is the temperature which exceeds the Tg of amorphous lactose when instantaneous stickiness occurs. The critical "X" values tor various dairy powders including WMP, SMP, MPC, whey protein, buttermilk, white cheese powder and GLUMP powder were found to be 33-49°C. 37-42°C. 42-51C. 50°C, 37-39°C, 28.5°C, and 40.7°C respectively. In addition, the slope of the trend line in the T-Tg plot, indicates how quickly the particular powder becomes sticky once the instantaneous sticky point has been exceeded. The particle-gun rig demonstrated that powders with greater than 30% amorphous lactose are more likely to cause blockage than powders with less than 30%. Both the critical 'X' value and the slope are unique to the powder. The stickiness curve was used to relate the powder surface stickiness condition with the drier outlet temperature and relative humidity. It was recommended to operate at conditions below the stickiness curve for a powder to avoid any chamber or cyclone blockages caused by stickiness. The slope enables a decision to be made about how close to the critical point a plant should be run for a particular powder. The inlet air temperature or concentrate feeding rate can be used to move the operating conditions towards or away from the stickiness curve, according to the operating situations

Cost stickiness revisited: Empirical aplication for farms

This article reviews previous research regarding cost stickiness and performs an empirical analysis applied to a sample of farms. It recognizes that modelization of cost stickiness is a particular case of representation of cost variations as a function of output variations. It also discusses methodological issues and analyses cost stickiness for all registered farm costs and opportunity costs of family work. Costs exhibit a considerable level of rigidity. Even for variable costs, a decrease in activity involves a lower decrease in costs than the amounts involved when activity increases. While registered indirect costs slightly decrease when activity decreases, opportunity costs always increase. The study provides empirical evidence that cost stickiness is significantly reduced with better management decision practices.cost stickiness, cost behavior, farm management accounting

Polydisperse fluid mixtures of adhesive colloidal particles

We investigate polydispersity effects on the average structure factor of colloidal suspensions of neutral particles with surface adhesion. A sticky hard sphere model alternative to Baxter's one is considered. The choice of factorizable stickiness parameters in the potential allows a simple analytic solution, within the ``mean spherical approximation'', for any number of components and arbitrary stickiness distribution. Two particular cases are discussed: i) all particles have different sizes but equal stickiness (Model I), and ii) each particle has a stickiness proportional to its size (Model II). The interplay between attraction and polydispersity yields a markedly different behaviour for the two Models in regimes of strong coupling (i.e. strong adhesive forces and low temperature) and large polydispersity. These results are then exploited to reanalyze experimental scattering data on sterically stabilized silica particles.Comment: 9 pages, 2 figures (included), Physica A (2001) to appea

The Evolution of Loan Rate Stickiness Across the Euro Area

To investigate the banking sector integration across euro area countries in terms of loan interest rate stickiness, we estimate structural loan rate curves for 12 euro area countries using time-varying regressions with stochastic volatility. Our results show that the loan rates are sticky to a policy interest rate in all countries for all loan maturities, the degree of stickiness differs across the countries, and the degree of difference is more prominent for longer loan maturities. For short-term loans, the loan rate stickiness decreases and for intermediate- and long-term loans the loan rate stickiness converge to average levels during the sample periods. Banking integration in the euro area is not yet complete, but the degree of heterogeneity in the loan rate stickiness decreases.banking integration, sticky loan interest rate, Bayesian analysis, time-varying regression, Markov chain Monte Carlo

Pervasive Stickiness

This paper explores a macroeconomic model of the business cycle in which stickiness of information is pervasive. We start from a familiar benchmark classical model and add to it the assumption that there is sticky information on the part of consumers, workers, and firms. We evaluate the model against three key facts that describe shortrun fluctuations: the acceleration phenomenon, the smoothness of real wages, and the gradual response of real variables to shocks. We find that pervasive stickiness is required to fit the facts. We conclude that models based on stickiness of information offer the promise of fitting the facts on business cycles while adding only one new plausible ingredient to the classical benchmark.

Characterising stickiness of dairy powders : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Bioprocess Engineering, Massey University

The stickiness phenomenon, one of the major operational problems, in the spray drying process is strongly related to changes in the powder particle surface. During the course of drying, powder particles with intermediate moisture pass through a very cohesive and adhesive 'plastic' phase. This phase has shown to be influenced by surface composition, moisture content, particle size, manufacturing method, surrounding air humidity and temperature. During spray drying, the powder particle experiences varied temperature and humidity conditions, which were replicated under controlled dynamic conditions to some extent in a 'Bench-top-scale Fluid Bed Rig' or in a 'Particle Gun Rig'. In these two set-ups, stickiness-end-point or deposition rates at a particular temperature and humidity combination were plotted to develop 'Stickiness Curves' after testing different dairy-based powders. Further improvements in the 'Particle Gun Rig' has been identified to minimise heat loss for future experimentation. It has been demonstrated that the stickiness property is a surface phenomenon. This is governed by the composition of a particular powder, manufacturing methods and the temperature / humidity conditions surrounding the powder particles. The low fat powders (42%) followed a combined 'Fat and lactose based stickiness model'. The 'lactose based model' followed the predicted glass transition (Tg) trend of amorphous lactose, shifted by some degree (X) upwards, depending on the product composition or the amount of amorphous lactose present - to be specific. These quick and easy methods to identify a safe and non-sticky operating window to minimise product adhesion to the equipment wall would be of huge benefit to the dairy industry in process optimization, as fore knowledge of likely difficulties and specified operating conditions will help efficient and economic operation. Attempts have been made to rectify the humidity tracking system in a spray drier and relate the 'stickiness curves' with its drying parameters. Further work should be done by taking commercial trial runs at recommended or allowable operating conditions with reference to 'Stickiness Curves', in order to maximise the throughput and to minimise the drying cost without compromising the product quality. Looking into the effects of other variables like air velocity, angle of impact, different impact surface materials and particle size on powder stickiness would be of much interest to the dairy industry