Coding for fast content download

Joshi, Gauri; Liu, Yanpei; Soljanin, Emina

doi:10.1109/allerton.2012.6483236

Cited by 96 publications

(108 citation statements)

References 22 publications

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“…The work in [21,22] studies FJ systems where jobs leave the system when a subset H ≤ N of its tasks are finished. This system is similar to the partial mapping FJ system that we study in Section 5, however, with subtle yet fundamental differences.…”

Section: Related Workmentioning

confidence: 99%

“…This system is similar to the partial mapping FJ system that we study in Section 5, however, with subtle yet fundamental differences. The FJ system presented in [21,22] is based on the assumption that when H tasks finish execution, the finished job purges the unfinished N − H tasks out their corresponding queues. The authors of [21,22] provide upper bounds for the mean response times in such systems under Poisson arrivals and general service distributions.…”

Section: Related Workmentioning

confidence: 99%

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Stochastic bounds in Fork–Join queueing systems under full and partial mapping

2016

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In a Fork-Join (FJ) queueing system an upstream fork station splits incoming jobs into N tasks to be further processed by N parallel servers, each with its own queue; the response time of one job is determined, at a downstream join station, by the maximum of the corresponding tasks' response times. This queueing system is useful to the modelling of multi-service systems subject to synchronization constraints, such as MapReduce clusters or multipath routing. Despite their apparent simplicity, FJ systems are hard to analyze.This paper provides the first computable stochastic bounds on the waiting and response time distributions in FJ systems under full (bijective) and partial (injective) mapping of tasks to servers. We consider four practical scenarios by combining 1a) renewal and 1b) non-renewal arrivals, and 2a) non-blocking and 2b) blocking servers. In the case of non-blocking servers we prove that delays scale as O(log N ), a law which is known for first moments under renewal input only. In the case of blocking servers, we prove that the same factor of log N dictates the stability region of the system. Simulation results indicate that our bounds are tight, especially at high utilizations, in all four scenarios. A remarkable insight gained from our results is that, at moderate to high utilizations, multipath routing "makes sense" from a queueing perspective for two paths only, i.e., response times drop the most when N = 2; the technical explanation is that the resequencing (delay) price starts to quickly dominate the tempting gain due to multipath transmissions.

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Section: Related Workmentioning

confidence: 99%

Section: Related Workmentioning

confidence: 99%

Stochastic bounds in Fork–Join queueing systems under full and partial mapping

2016

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“…6, we plot p cover , respectively). The exact probability for an uncoded cyclic placement is found using the coverage condition (2), and in this case it coincides with p cyc cover . We also plot p cyc sim , the only graph in Fig.…”

Section: Design Placementmentioning

confidence: 99%

“…the survey in [1]. In [2], [3], the effect of MDS coding on content download time was analyzed for two content access models, where an improvement in performance was achieved. In [4], latency delay was reduced by choosing MDS codes of appropriate rates.…”

Section: Introductionmentioning

confidence: 99%

Coding for Improved Throughput Performance in Network Switches

Cohen

Cassuto

2017

IEEE/ACM Trans. Networking

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Network switches and routers need to serve packet writes and reads at rates that challenge the most advanced memory technologies. As a result, scaling the switching rates is commonly done by parallelizing the packet I/Os using multiple memory units. For improved read rates, packets can be coded upon write, thus giving more flexibility at read time to achieve higher utilization of the memory units. This paper presents a detailed study of coded network switches, and in particular how to design them to maximize the throughput advantages over standard uncoded switches. Toward that objective the paper contributes a variety of algorithmic and analytical tools to improve and evaluate the throughput performance. The most interesting finding of this study is that the placement of packets in the switch memory is the key to both high performance and algorithmic efficiency. One particular placement policy we call "design placement" is shown to enjoy the best combination of throughput performance and implementation feasibility.

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“…$15.00 DOI: 10.1145/nnnnnnn.nnnnnnn simultaneously download from di erent replicas, or each user can issue simultaneous requests to multiple replicas and wait for the rst download to nish [6,7,15]. Data access systems arising in erasure coded storage have received a lot of a ention for all-data (see for example [12,14,19,24] and references therein) and some for hot-data download [16,17], and usually involve single or multiple inter-dependent fork-join queueing systems.…”

Section: Introductionmentioning

confidence: 99%

Simplex Queues for Hot-Data Download

Aktas

Najm

Soljanin

2017

SIGMETRICS Perform. Eval. Rev.

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In cloud storage systems, hot data is usually replicated over multiple disks/servers in order to accommodate simultaneous access by multiple users as well as increase the fault tolerance of the system. Recent cloud storage research has proposed using availability codes, which is a special class of erasure codes, as a more storagee cient way to store hot data. ese codes enable data recovery from multiple, small disjoint groups of servers. e number of the recovery groups is referred to as the availability and the size of each group as the locality of the code. Up till now, we have very limited knowledge on how code locality and availability a ect data access time. Data download from these systems involves multiple fork-join queues operating in-parallel, making the analysis of access time a very challenging problem.In this paper, we present an analysis of average data access time in storage systems employing simplex codes, which are an important, in certain sense optimal, class of availability codes. We generalize the analysis for codes with locality 2 and any degree of availability. Speci cally, using a queueing theoretic approach, we derive bounds and approximations on the average response time for two di erent Poisson request arrival models. We also compare two scheduling strategies for reduced access time and load balancing.

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Coding for fast content download

Cited by 96 publications

References 22 publications

Stochastic bounds in Fork–Join queueing systems under full and partial mapping

Stochastic bounds in Fork–Join queueing systems under full and partial mapping

Coding for Improved Throughput Performance in Network Switches

Simplex Queues for Hot-Data Download

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