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Power and performance management of virtualized computing environments via lookahead control.
- In Proc. Fifth Int’l Conference on Autonomic Computing,
, 2008
"... Abstract There is growing incentive to reduce the power consumed by large-scale data centers that host online services such as banking, retail commerce, and gaming. Virtualization is a promising approach to consolidating multiple online services onto a smaller number of computing resources. A virtu ..."
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Cited by 138 (6 self)
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Abstract There is growing incentive to reduce the power consumed by large-scale data centers that host online services such as banking, retail commerce, and gaming. Virtualization is a promising approach to consolidating multiple online services onto a smaller number of computing resources. A virtualized server environment allows computing resources to be shared among multiple performance-isolated platforms called virtual machines. By dynamically provisioning virtual machines, consolidating the workload, and turning servers on and off as needed, data center operators can maintain the desired quality-of-service (QoS) while achieving higher server utilization and energy efficiency. We implement and validate a dynamic resource provisioning framework for virtualized server environments wherein the provisioning problem is posed as one of sequential optimization under uncertainty and solved using a lookahead control scheme. The proposed approach accounts for the switching costs incurred while provisioning virtual machines and explicitly encodes the corresponding risk in the optimization problem. Experiments using the Trade6 enterprise application show that a server cluster managed by the controller conserves, on average, 22% of the power required by a system without dynamic control while still maintaining QoS goals. Finally, we use trace-based simulations to analyze controller performance on server clusters larger than our testbed, and show how concepts from approximation theory can be used to further reduce the computational burden of controlling large systems.
Write Off-Loading: Practical Power Management for Enterprise Storage
"... In enterprise data centers power usage is a problem impacting server density and the total cost of ownership. Storage uses a significant fraction of the power budget and there are no widely deployed power-saving solutions for enterprise storage systems. The traditional view is that enterprise worklo ..."
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Cited by 134 (9 self)
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In enterprise data centers power usage is a problem impacting server density and the total cost of ownership. Storage uses a significant fraction of the power budget and there are no widely deployed power-saving solutions for enterprise storage systems. The traditional view is that enterprise workloads make spinning disks down ineffective because idle periods are too short. We analyzed block-level traces from 36 volumes in an enterprise data center for one week and concluded that significant idle periods exist, and that they can be further increased by modifying the read/write patterns using write off-loading. Write off-loading allows write requests on spun-down disks to be temporarily redirected to persistent storage elsewhere in the data center. The key challenge is doing this transparently and efficiently at the block level, without sacrificing consistency or failure resilience. We describe our write offloading design and implementation that achieves these goals. We evaluate it by replaying portions of our traces on a rack-based testbed. Results show that just spinning disks down when idle saves 28–36 % of energy, and write off-loading further increases the savings to 45–60%. 1
Pergamum: Replacing tape with energy efficient, reliable, disk-based archival storage
- IN FAST-2008: 6TH USENIX CONFERENCE ON FILE AND STORAGE TECHNOLOGIES
, 2008
"... As the world moves to digital storage for archival purposes, there is an increasing demand for reliable, lowpower, cost-effective, easy-to-maintain storage that can still provide adequate performance for information retrieval and auditing purposes. Unfortunately, no current archival system adequatel ..."
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Cited by 64 (14 self)
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As the world moves to digital storage for archival purposes, there is an increasing demand for reliable, lowpower, cost-effective, easy-to-maintain storage that can still provide adequate performance for information retrieval and auditing purposes. Unfortunately, no current archival system adequately fulfills all of these requirements. Tape-based archival systems suffer from poor random access performance, which prevents the use of inter-media redundancy techniques and auditing, and requires the preservation of legacy hardware. Many diskbased systems are ill-suited for long-term storage because their high energy demands and management requirements make them cost-ineffective for archival purposes. Our solution, Pergamum, is a distributed network of intelligent, disk-based, storage appliances that stores data reliably and energy-efficiently. While existing MAID systems keep disks idle to save energy, Pergamum adds NVRAM at each node to store data signatures, metadata, and other small items, allowing deferred writes, metadata requests and inter-disk data verification to be performed while the disk is powered off. Pergamum uses both intra-disk and inter-disk redundancy to guard against data loss, relying on hash tree-like structures of algebraic signatures to efficiently verify the correctness of stored data. If failures occur, Pergamum uses staggered rebuild to reduce peak energy usage while rebuilding large redundancy stripes. We show that our approach is comparable in both startup and ongoing costs to other archival technologies and provides very high reliability. An evaluation of our implementation of Pergamum shows that it provides adequate performance.
A nine year study of file system and storage benchmarking
- ACM Transactions on Storage
, 2008
"... Benchmarking is critical when evaluating performance, but is especially difficult for file and storage systems. Complex interactions between I/O devices, caches, kernel daemons, and other OS components result in behavior that is rather difficult to analyze. Moreover, systems have different features ..."
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Cited by 55 (8 self)
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Benchmarking is critical when evaluating performance, but is especially difficult for file and storage systems. Complex interactions between I/O devices, caches, kernel daemons, and other OS components result in behavior that is rather difficult to analyze. Moreover, systems have different features and optimizations, so no single benchmark is always suitable. The large variety of workloads that these systems experience in the real world also adds to this difficulty. In this article we survey 415 file system and storage benchmarks from 106 recent papers. We found that most popular benchmarks are flawed and many research papers do not provide a clear indication of true performance. We provide guidelines that we hope will improve future performance evaluations. To show how some widely used benchmarks can conceal or overemphasize overheads, we conducted a set of experiments. As a specific example, slowing down read operations on ext2 by a factor of 32 resulted in only a 2–5 % wall-clock slowdown in a popular compile benchmark. Finally, we discuss future work to improve file system and storage benchmarking.
SRCMap: Energy Proportional Storage using Dynamic Consolidation
"... We investigate the problem of creating an energy proportional storage system through power-aware dynamic storage consolidation. Our proposal, Sample-Replicate-Consolidate Mapping (SRCMap), is a storage virtualization layer optimization that enables energy proportionality for dynamic I/O workloads by ..."
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Cited by 41 (9 self)
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We investigate the problem of creating an energy proportional storage system through power-aware dynamic storage consolidation. Our proposal, Sample-Replicate-Consolidate Mapping (SRCMap), is a storage virtualization layer optimization that enables energy proportionality for dynamic I/O workloads by consolidating the cumulative workload on a subset of physical volumes proportional to the I/O workload intensity. Instead of migrating data across physical volumes dynamically or replicating entire volumes, both of which are prohibitively expensive, SRCMap samples a subset of blocks from each data volume that constitutes its working set and replicates these on other physical volumes. During a given consolidation interval, SRCMap activates a minimal set of physical volumes to serve the workload and spins down the remaining volumes, redirecting their workload to replicas on active volumes. We present both theoretical and experimental evidence to establish the effectiveness of SRCMap in minimizing the power consumption of enterprise storage systems. 1
Sierra: a power-proportional, distributed storage system
"... We present the design, implementation, and evaluation of Sierra: a power-proportional, distributed storage system. I/O workloads in data centers show significant diurnal variation, with peak and trough periods. Sierra powers down storage servers during the troughs. The challenge is to ensure that da ..."
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Cited by 30 (1 self)
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We present the design, implementation, and evaluation of Sierra: a power-proportional, distributed storage system. I/O workloads in data centers show significant diurnal variation, with peak and trough periods. Sierra powers down storage servers during the troughs. The challenge is to ensure that data is available for reads and writes at all times, including power-down periods. Consistency and fault-tolerance of the data, as well as good performance, must also be maintained. Sierra achieves all these through a set of techniques including power-aware layout, predictive gear scheduling, and a replicated shortterm versioned store. Replaying live server traces from a large e-mail service (Hotmail) shows power savings of at least 23%, and analysis of load from a small enterprise shows that power savings of up to 60 % are possible. 1
Cost Effective Storage using Extent Based Dynamic Tiering
"... Multi-tier systems that combine SSDs with SAS/FC and/or SATA disks mitigate the capital cost burden of SSDs, while benefiting from their superior I/O performance per unit cost and low power. Though commercial SSD-based multi-tier solutions are available, configuring such a system with the optimal nu ..."
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Cited by 27 (4 self)
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Multi-tier systems that combine SSDs with SAS/FC and/or SATA disks mitigate the capital cost burden of SSDs, while benefiting from their superior I/O performance per unit cost and low power. Though commercial SSD-based multi-tier solutions are available, configuring such a system with the optimal number of devices per tier to achieve performance goals at minimum cost remains a challenge. Furthermore, these solutions do not leverage the opportunity to dynamically consolidate load and reduce power/operating cost. Our extent-based dynamic tiering solution, EDT, addresses these limitations via two key components of its design. A Configuration Adviser EDT-CA determines the adequate mix of storage devices to buy and install to satisfy a given workload at minimum cost, and a Dynamic Tier Manager EDT-DTM performs dynamic extent placement once the system is running to satisfy performance requirements while minimizing dynamic power consumption. Key to the cost minimization of EDT-CA is its ability to simulate the dynamic extent placement afforded by EDT-DTM. Key to the overall effectiveness of EDT-DTM is its ability to consolidate load within tiers when feasible, rapidly respond to unexpected changes in the workload, and carefully control the overhead due to extent migration. Our results using production workloads show that EDT incurs lower capital and operating cost, consumes less power, and delivers similar or better performance relative to SAS-only storage systems as well as other simpler approaches to extent-based tiering. 1
WorkOut: I/O Workload Outsourcing for Boosting RAID Reconstruction Performance
"... User I/O intensity can significantly impact the performance of on-line RAID reconstruction due to contention for the shared disk bandwidth. Based on this observation, this paper proposes a novel scheme, called WorkOut (I/O Workload Outsourcing), to significantly boost RAID reconstruction performance ..."
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Cited by 17 (1 self)
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User I/O intensity can significantly impact the performance of on-line RAID reconstruction due to contention for the shared disk bandwidth. Based on this observation, this paper proposes a novel scheme, called WorkOut (I/O Workload Outsourcing), to significantly boost RAID reconstruction performance. WorkOut effectively outsources all write requests and popular read requests originally targeted at the degraded RAID set to a surrogate RAID set during reconstruction. Our lightweight prototype implementation of WorkOut and extensive tracedriven and benchmark-driven experiments demonstrate that, compared with existing reconstruction approaches, WorkOut significantly speeds up both the total reconstruction time and the average user response time. Importantly, WorkOut is orthogonal to and can be easily incorporated into any existing reconstruction algorithms. Furthermore, it can be extended to improving the performance of other background support RAID tasks, such as re-synchronization and disk scrubbing. 1
Energy Proportionality for Storage: Impact and Feasibility
"... (in alphabetical order) This paper highlights the growing importance of storage energy consumption in a typical data center, and asserts that storage energy research should drive towards a vision of energy proportionality for achieving significant energy savings. Our analysis of real-world enterpris ..."
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Cited by 13 (2 self)
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(in alphabetical order) This paper highlights the growing importance of storage energy consumption in a typical data center, and asserts that storage energy research should drive towards a vision of energy proportionality for achieving significant energy savings. Our analysis of real-world enterprise workloads shows a potential energy reduction of 40-75% using an ideally proportional system. We then present a preliminary analysis of appropriate techniques to achieve proportionality, chosen to match both application requirements and workload characteristics. Based on the techniques we have identified, we believe that energy proportionality is achievable in storage systems at a time scale that will make sense in real world environments. 1
GreenFS: Making Enterprise Computers Greener by Protecting Them Better ABSTRACT
"... Hard disks contain data—frequently an irreplaceable asset of high monetary and non-monetary value. At the same time, hard disks are mechanical devices that consume power, are noisy, and fragile when their platters are rotating. In this paper we demonstrate that hard disks cause different kinds of pr ..."
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Cited by 12 (0 self)
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Hard disks contain data—frequently an irreplaceable asset of high monetary and non-monetary value. At the same time, hard disks are mechanical devices that consume power, are noisy, and fragile when their platters are rotating. In this paper we demonstrate that hard disks cause different kinds of problems for different types of computer systems and demystify several common misconceptions. We show that solutions developed to date are incapable of solving the power consumption, noise, and data reliability problems without sacrificing hard disk life-time, data reliability, or user convenience. We considered data reliability, recovery, performance, user convenience, and hard disk-caused problems together at the enterprise scale. We have designed GreenFS: a fan-out stackable file system that offers all-time all-data run-time data protection, improves performance under typical user workloads, and allows hard disks to be kept off most of the time. As a result, GreenFS improves enterprise data protection, minimizes disk drive-related power consumption and noise and increases the chances of disk drive survivability in case of unexpected external impacts.
