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56
Load Balancing and Unbalancing for Power and Performance in Cluster-Based Systems
, 2001
"... In this paper we address power conservation for clusters of workstations or PCs. Our approach is to develop systems that dynamically turn cluster nodes on -- to be able to handle the load imposed on the system efficiently -- and off -- to save power under lighter load. The key component of our syst ..."
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Cited by 194 (10 self)
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In this paper we address power conservation for clusters of workstations or PCs. Our approach is to develop systems that dynamically turn cluster nodes on -- to be able to handle the load imposed on the system efficiently -- and off -- to save power under lighter load. The key component of our systems is an algorithm that makes load balancing and unbalancing decisions by considering both the total load imposed on the cluster and the power and performance implications of turning nodes off. The algorithm is implemented in two different ways: (1) at the application level for a cluster-based, localityconscious network server; and (2) at the operating system level for an operating system for clustered cycle servers. Our experimental results are very favorable, showing that our systems conserve both power and energy in comparison to traditional systems.
Scalable Content-aware Request Distribution in Cluster-based Network Servers
- IN PROCEEDINGS OF THE USENIX 2000 ANNUAL TECHNICAL CONFERENCE
, 2000
"... We present a scalable architecture for content-aware request distribution in Web server clusters. In this architecture, a level-4 switch acts as the point of contact for the server on the Internet and distributes the incoming requests to a number of back-end nodes. The switch does not perform any c ..."
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Cited by 157 (3 self)
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We present a scalable architecture for content-aware request distribution in Web server clusters. In this architecture, a level-4 switch acts as the point of contact for the server on the Internet and distributes the incoming requests to a number of back-end nodes. The switch does not perform any content-based distribution. This function is performed by each of the back-end nodes, which may forward the incoming request to another back-end based on the requested content. In terms of scalability, this architecture compares favorably to existing approaches where a front-end node performs content-based distribution. In our architecture, the expensive operations of TCP connection establishment and hando are distributed among the back-ends, rather than being centralized in the front-end node. Only a minimal additional latency penalty is paid for much improved scalability. We have implemented this new architecture, and we demonstrate its superior scalability by comparing it to a system tha...
Dynamic Load Balancing on Web-server Systems
- IEEE Internet Computing
, 1999
"... Popular Web sites can neither rely on a single powerful server nor on independent mirroredservers to support the ever increasing request load. Scalability and availability can be provided by distributed Web-server architectures that schedule client requests among the multiple server nodes in a user- ..."
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Cited by 152 (6 self)
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Popular Web sites can neither rely on a single powerful server nor on independent mirroredservers to support the ever increasing request load. Scalability and availability can be provided by distributed Web-server architectures that schedule client requests among the multiple server nodes in a user-transparent way. In this paper we will review the state of the art in load balancing techniques on distributed Web-server systems. We will analyze the efficiency and limitations of the various approaches and their tradeoff.
Energy Conservation in Heterogeneous Server Clusters
- PPoPP'05
, 2005
"... The previous research on cluster-based servers has focused on homogeneous systems. However, real-life clusters are almost invariably heterogeneous in terms of the performance, capacity, and power consumption of their hardware components. In this paper, we argue that designing efficient servers for h ..."
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Cited by 112 (5 self)
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The previous research on cluster-based servers has focused on homogeneous systems. However, real-life clusters are almost invariably heterogeneous in terms of the performance, capacity, and power consumption of their hardware components. In this paper, we argue that designing efficient servers for heterogeneous clusters requires defining an efficiency metric, modeling the different types of nodes with respect to the metric, and searching for request distributions that optimize the metric. To concretely illustrate this process, we design a cooperative Web server for a heterogeneous cluster that uses modeling and optimization to minimize the energy consumed per request. Our experimental results for a cluster comprised of traditional and blade nodes show that our server can consume 42 % less energy than an energyoblivious server, with only a negligible loss in throughput. The results also show that our server conserves 45 % more energy than an energy-conscious server that was previously proposed for homogeneous clusters.
Live wide-area migration of virtual machines including local persistent state
- In VEE ’07: Proceedings of the 3rd international conference on Virtual execution environments (New
"... So far virtual machine (VM) migration has focused on transferring the run-time memory state of the VMs in local area networks (LAN). However, for wide-area network (WAN) migration it is crucial to not just transfer the VMs image but also transfer its local persistent state (its file system) and its ..."
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Cited by 96 (5 self)
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So far virtual machine (VM) migration has focused on transferring the run-time memory state of the VMs in local area networks (LAN). However, for wide-area network (WAN) migration it is crucial to not just transfer the VMs image but also transfer its local persistent state (its file system) and its on-going network connections. In this paper we address both: by combining a blocklevel solution with pre-copying and write throttling we show that we can transfer an entire running web server, including its local persistent state, with minimal disruption — three seconds in the LAN and 68 seconds in the WAN); by combining dynDNS with tunneling, existing connections can continue transparently while new ones are redirected to the new network location. Thus we show experimentally that by combining well-known techniques in a novel manner we can provide system support for migrating virtual execution environments in the wide area.
Dynamic Cluster Reconfiguration For Power And Performance
, 2002
"... In this paper we address power conservation for clusters of workstations or PCs. Our approach is to develop systems that dynamically turn cluster nodes on -- to be able to handle the load imposed on the system efficiently -- and off -- to save power under lighter load. The key component of our syste ..."
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Cited by 91 (9 self)
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In this paper we address power conservation for clusters of workstations or PCs. Our approach is to develop systems that dynamically turn cluster nodes on -- to be able to handle the load imposed on the system efficiently -- and off -- to save power under lighter load. The key component of our systems is an algorithm that makes cluster reconfiguration decisions by considering the total load imposed on the system and the power and performance implications of changing the current configuration. The algorithm is implemented in two common cluster-based systems: a network server and an operating system for clustered cycle servers. Our experimental results are very favorable, showing that our systems conserve both power and energy in comparison to traditional systems.
Critical Path Analysis of TCP Transactions
- IEEE/ACM Transactions on Networking
, 2000
"... Improving the performance of data transfers in the Internet (such as Web transfers) requires a detailed understanding of when and how delays are introduced. Unfortunately, the complexity of data transfers like those using HTTP is great enough that identifying the precise causes of delays is difficul ..."
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Cited by 89 (3 self)
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Improving the performance of data transfers in the Internet (such as Web transfers) requires a detailed understanding of when and how delays are introduced. Unfortunately, the complexity of data transfers like those using HTTP is great enough that identifying the precise causes of delays is difficult. In this paper we describe a method for pinpointing where delays are introduced into applications like HTTP by using critical path analysis. By constructing and pro ling the critical path, it is possible to determine what fraction of total transfer latency is due to packet propagation, network variation (e.g., queuing at routers or route uctuation), packet losses, and delays at the server and at the client. We have implemented our technique in a tool called tcpeval that automates critical path analysis for Web transactions. We show that our analysis method is robust enough to analyze traces taken for two different TCP implementations (Linux and FreeBSD). To demonstrate the utility of our approach, we present the results of critical path analysis for a set of Web transactions taken over 14 days under a variety of server and network conditions. The results show that critical path analysis can shed considerable light on the causes of delays in Web transfers, and can expose subtleties in the behavior of the entire end-to-end system.
Efficiency vs. Portability in Cluster-Based Network Servers
"... Efficiency and portability are usually conflicting objectives for cluster-based network servers that distribute the clients ’ requests across the cluster based on the actual content requested. Our work is based on the observation that this efficiency vs. portability tradeoff has not been discussed b ..."
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Cited by 52 (21 self)
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Efficiency and portability are usually conflicting objectives for cluster-based network servers that distribute the clients ’ requests across the cluster based on the actual content requested. Our work is based on the observation that this efficiency vs. portability tradeoff has not been discussed before in the literature. To fill this gap, in this paper we study this tradeoff in the context of an interesting class of content-based network servers, the locality-conscious servers, using modeling and experimentation. Our analytical model gauges the potential performance benefits of portable and non-portable localityconscious request distribution with respect to a traditional, locality-oblivious server, as a function of multiple parameters. Based on our experience with the model, we design and evaluate a portable, locality-conscious server. Experiments with our server, a nonportable server, and a traditional server validate and confirm our modeling results under several real workloads. Based on our modeling and experimental results, our main conclusion is that portability should be promoted in cluster-based network servers with low processor overhead communication, given its relatively low cost 15%) in terms of efficiency. For clusters with high processor overhead communication, efficiency should be the overriding concern, as the cost of portability can be very high (as high as 98 % on 32 nodes). We also conclude that user-level communication can be useful even for non-scientific applications such as network servers.
Load Balancing a Cluster of Web Servers - Using Distributed Packet Rewriting
- Proceedings of the 2000 IEEE International Performance, Computing, and Communications Conference
, 2000
"... In this paper, we present and evaluate an implementation of a prototype scalable web server. The prototype consists of a load-balanced cluster of hosts that collectively accept and service TCP connections. The host IP addresses are advertised using the Round Robin DNS (RR-DNS) technique, allowing ..."
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Cited by 47 (1 self)
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In this paper, we present and evaluate an implementation of a prototype scalable web server. The prototype consists of a load-balanced cluster of hosts that collectively accept and service TCP connections. The host IP addresses are advertised using the Round Robin DNS (RR-DNS) technique, allowing any host to receive requests from any client. Once a client attempts to establish a TCP connection with one of the hosts, a decision is made as to whether or not the connection should be redirected to a different host---namely, the host with the lowest number of established connections. We use the low-overhead Distributed Packet Rewriting (DPR) technique [Bestavros, Crovella, Liu, and Martin 1998] to redirect TCP connections. In our prototype, each host keeps information about the remaining hosts in the system. Load information is maintained using periodic multicast amongst the cluster hosts. Performance measurements suggest that our prototype outperforms both pure RR-DNS and the sta...
Analytical and Experimental Evaluation of Cluster-Based Network Servers
- World Wide Web Journal
, 1999
"... In this paper we use analytic modeling and simulation to evaluate network servers implemented on clusters of workstations. More specifically, we model the potential benefits of locality-conscious request distribution within the cluster and evaluate the performance of a cluster-based server (called L ..."
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Cited by 30 (13 self)
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In this paper we use analytic modeling and simulation to evaluate network servers implemented on clusters of workstations. More specifically, we model the potential benefits of locality-conscious request distribution within the cluster and evaluate the performance of a cluster-based server (called L2S) we designed in light of our experience with the model. Our most important modeling results show that locality-conscious distribution on a 16-node cluster can increase server throughput with respect to a locality-oblivious server by up to 5-fold, depending on the average size of the files requested and on the size of the server's working set. Our simulation results demonstrate that L2S achieves throughput that is within 28% of the full potential of locality-conscious distribution on 16 nodes, outperforming and significantly outscaling the best-known locality-conscious server. Based on our results and on the fact that the files serviced by network servers are becoming larger and more numer...
