Disk scheduling for mixed-media workloads in a multimedia server (original) (raw)
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Scalable multimedia disk scheduling
Proceedings. 20th International Conference on Data Engineering, 2004
A new multimedia disk scheduling algorithm, termed Cascaded-SFC, is presented. The Cascaded-SFC multimedia disk scheduler is applicable in environments where multimedia data requests arrive with different quality of service (QoS) requirements such as real-time deadline and user priority. Previous work on disk scheduling has focused on optimizing the seek times and/or meeting the real-time deadlines. The Cascaded-SFC disk scheduler provides a unified framework for multimedia disk scheduling that scales with the number of scheduling parameters. The general idea is based on modeling the multimedia disk requests as points in multiple multi-dimensional sub-spaces, where each of the dimensions represents one of the parameters (e.g., one dimension represents the request deadline, another represents the disk cylinder number, and a third dimension represents the priority of the request, etc.). Each multi-dimensional sub-space represents a subset of the QoS parameters that share some common scheduling characteristics. Then the multimedia disk scheduling problem reduces to the problem of finding a linear order to traverse the multi-dimensional points in each sub-space. Multiple space-filling curves are selected to fit the scheduling needs of the QoS parameters in each sub-space. The orders in each sub-space are integrated in a cascaded way to provide a total order for the whole space. Comprehensive experiments demonstrate the efficiency and scalability of the Cascaded-SFC disk scheduling algorithm over other disk schedulers.
Clustered scheduling algorithms for mixed-media disk workloads in a multimedia server
2003
Divisible load scenarios occur in modern media server applications since most multimedia applications typically require access to continuous and discrete data. A high performance Continuous Media (CM) server greatly depends on the ability of its disk IO subsystem to serve both types of workloads efficiently. Disk scheduling algorithms for mixed media workloads, although they play a central role in this task, have been overlooked by related research efforts. These algorithms must satisfy several stringent performance goals, such as achieving low response time and ensuring fairness, for the discrete-data workload, while at the same time guaranteeing the uninterrupted delivery of continuous data, for the continuous-data workload. The focus of this paper is on disk scheduling algorithms for mixed media workloads in a multimedia information server. We propose novel algorithms, present a taxonomy of relevant algorithms, and study their performance through experimentation. Our results show that our algorithms offer drastic improvements in discrete request average response times, are fair, serve continuous requests without interruptions, and that the disk technology trends are such that the expected performance benefits can be even greater in the future.
A continuum of disk scheduling algorithms
ACM Transactions on Computer Systems, 1987
A continuum of disk scheduling algorithms, V(R), having endpoints V(0) = SSTF and V(1) = SCAN, is defined. V(R) maintains a current SCAN direction (in or out) and services next the request with the smallest effective distance. The effective distance of a request that lies in the current direction is its physical distance (in cylinders) from the read/write head. The effective distance of a request in the opposite direction is its physical distance plus R X (total number of cylinders on the disk). By use of simulation methods, it is shown that this definitional continuum also provides a continuum in performance, both with respect to the mean and with respect to the standard deviation of request waiting time. For objective functions that are linear combinations of the two measures, pw + kuw, intermediate points of the continuum are seen to provide performance uniformly superior to both SSTF and SCAN. A method of implementing V(R) and the results of its experimental use in a real system are presented.
Major Half Served First (MHSF) Disk Scheduling Algorithm
I/O performance has been improved by proper scheduling of disk accesses since the time movable head disk came into existence. Disk scheduling is the process of carefully examining the pending requests to determine the most efficient way to service the pending requests. Scheduling algorithms generally concentrate on reducing seek times for a set of requests, because seek times tend to be an order of magnitude greater than latency times. Some important scheduling algorithms are First-Come-First-Served (FCFS), Shortest Seek Time First (SSTF), SCAN, Circular Scan (C-SCAN) and LOOK. This paper proposes a new disk scheduling algorithm called Major Half Served First (MHSF). Simulation results show that using MHSF the service is fast and seek time has been reduced drastically.
A Novel Deadline Driven Disk Scheduling Algorithm for Multi-Priority Multimedia Objects
International Conference on Data Engineering, 2000
In this paper we introduce a new deadline driven diskscheduling algorithm designed for multimedia servers.The proposed algorithm supports real time requestswith multiple priorities, e.g., those for di#erent objectclasses in digital library applications. The proposedalgorithm enhances utilization of disk bandwidthby #a# maintaining one queue for all requests, and #b#optimizing the seek time. Prior schemes, collectivelytermed #Multi-queue schemes", maintain a separatequeue for
A Comparative Analysis of Disk Scheduling Algorithms
International Journal for Research in Applied Sciences and Biotechnology, 2021
In an operating system, disk scheduling is the process of managing the I/O request to the secondary storage devices such as hard disk. The speed of the processor and primary memory has increased in a rapid way than the secondary storage. Seek time is the important factor in an operating system to get the best access time. For the better performance, speedy servicing of I/O request for secondary memory is very important. The goal of the disk-scheduling algorithm is to minimize the response time and maximize throughput of the system. This work analyzed and compared various basic disk scheduling techniques like First Come First Serve (FCFS), Shortest Seek Time First (SSTF), SCAN, LOOK, Circular SCAN (C-SCAN) and Circular LOOK (C-LOOK) along with the corresponding seek time. From the comparative analysis, the result show that C-LOOK algorithm give the least head movement and seek time in different cases as compared to other algorithm. Therefore, it maximizes the throughput for the storage devices.
A hierarchical disk scheduler for multimedia systems
Future Generation Computer Systems, 2003
An integrated storage platform for open systems should be able to meet the requirements of deterministic applications, multimedia systems, and traditional best-effort applications. It should also provide a scheduling mechanism fitting all those types of applications. In this paper, we propose a two-level hierarchical disk scheduling scheme, named 2-Q, which can guarantee deterministic deadlines, maximize the number of statistic real-time streams processed by the disk system, and minimize the average latency for best-effort requests. The upper level of the scheduling architecture, server level, is divided into three queues: deterministic, statistic, and best-effort requests. Each server may have its own scheduling algorithm. The lower level, disk driver, chooses the ready streams using its own scheduling criteria. We also propose an adaptive admission control algorithm relying on worst and average values of disk server utilization. Only streams satisfying the admission algorithm criteria are accepted for further processing by the disk server. The solution is extended to a parallel disk system by using a third hierarchical level, named meta-scheduler, briefly described in the paper. The performance evaluations demonstrate that our scheduling architecture is adequated for handling stream sets with different deterministic, statistic, or best-effort requirements.
IJARCSMS
To service a request, a disk system requires that the head be moved to the desired track, then a wait for latency and finally the transfer of data.
CSched : Real-time disk scheduling with concurrent I/O request
2011
We present a new real-time disk scheduling algorithm, Concurrent Scheduler or CSched, which maximizes throughput for modern storage devices while providing real-time access guarantees, with computational costs of O(log n). To maximize performance it ensures request concurrency at the device and maximizes the depth of a new Limited Cyclical SCAN (L-CSCAN) queue that optimizes the request sequence sent to the device. For realtime requests there is an additional SCAN-EDF queue in front of the L-CSCAN queue to absorb bursts of realtime requests until they can be drained to the L-CSCAN queue. The real-time guarantees are provided by managing the worst-case latency at each stage of the pipeline: SCAN-EDF, L-CSCAN, and device. CSched is configured by the tuple {λ, σ, δ, τ(r), N}, where λ and σ are the minimal initial slack time and workload burstiness and are properties of the workload, and where δ, τ(r), and N are the deviceworst-case latency, worst-case throughput rate time for a request, and maximal number of concurrent requests, and are experimentally determined properties of the storage device. An experimental evaluation of CSched shows that given sufficient initial slack time, the system throughput performance costs of providing real-time guarantees are negligible.