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Bakhshi Valojerdi, Zeinab
Alternative names
Publications (10 of 13) Show all publications
Bakhshi, Z., Rodriguez-Navas, G. & Hansson, H. (2023). Analyzing the performance of persistent storage for fault-tolerant stateful fog applications. Journal of systems architecture, 144, Article ID 103004.
Open this publication in new window or tab >>Analyzing the performance of persistent storage for fault-tolerant stateful fog applications
2023 (English)In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 144, article id 103004Article in journal (Refereed) Published
Abstract [en]

In this paper, we analyze the scalability and performance of a persistent, fault-tolerant storage approach that provides data availability and consistency in a distributed container-based architecture with intended use in industrial control applications. We use simulation to evaluate the performance of this storage system in terms of scalability and failures. As the industrial applications considered have timing constraints, the simulation results show that for certain failure patterns, it is possible to determine whether the storage solution can meet critical deadlines. The presented approach is applicable for evaluating timing constraints also of other container-based critical applications that require persistent storage.

National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-64563 (URN)10.1016/j.sysarc.2023.103004 (DOI)001091755600001 ()2-s2.0-85173500699 (Scopus ID)
Funder
EU, Horizon 2020Vinnova, 2018-02437
Available from: 2023-10-20 Created: 2023-10-20 Last updated: 2023-12-04Bibliographically approved
Bakhshi, Z. (2023). Lightweight Persistent Storage for Industrial Applications. (Doctoral dissertation). Västerås: Mälardalen University
Open this publication in new window or tab >>Lightweight Persistent Storage for Industrial Applications
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Clouds are large computer centers that offer remote access to computing and storage resources, making them popular for business and web applications. They are now being considered for use in safety-critical applications such as factories, but lack sufficient time predictability, which makes it challenging to use them in these time-sensitive applications. To overcome this limitation, an intermediate layer, the fog layer, is introduced to provide computational resources closer to the network edge. However, this new computing paradigm faces its own challenges in resource management, scalability, and reliability due to resource constrained nodes. Lightweight virtualization technologies like containerization can solve the performance-reliability dichotomy in fog computing and provide built-in fault tolerance mechanisms. By studying a robotic use-case, we realized the critical importance of persistent data storage for stateful applications, such as many control applications. However, container-based solutions lack fault-tolerant persistent storage. In this thesis, we identify new challenges associated with leveraging container-based architectures, particularly the importance of persistent storage for stateful applications. We investigate the design possibilities for persistent fault-tolerant storage and propose a solution adapted to container-based fog architectures and tailored for stateful applications. The solution provides scalability, auto recovery, and re-integration after failures at application and node levels. Key elements are a replicated data structure and a storage container, using a consensus protocol for distributed data consistency and fault tolerance in case of node failures. The fault tolerance and consistency of the solution are modeled and verified, and its timing requirements evaluated. We use simulation to evaluate the timing performance of our solution in larger set-ups. The results of our study show that although adding a consistency protocol introduces a timing overhead, the solution still meets timing requirements for the studied use-case even in presence of a set of relevant faults. By leveraging a four-dimensional approach, we also conduct a comparative analysis of our solution with other approaches from various perspectives, indicating that our solution can be applied in a broader context than initially intended.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2023
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 394
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:mdh:diva-64555 (URN)978-91-7485-617-0 (ISBN)
Public defence
2023-12-11, Milos, Mälardalens universitet, Västerås, 13:15 (English)
Opponent
Supervisors
Available from: 2023-10-23 Created: 2023-10-19 Last updated: 2023-11-20Bibliographically approved
Beqiri, L., Bakhshi Valojerdi, Z., Punnekkat, S. & Cicchetti, A. (2023). Remaining Useful Life Estimation for Railway Gearbox Bearings Using Machine Learning. In: Lecture Notes in Computer Science: . Paper presented at 5th International conference on Reliability, Safety and Security of Railway Systems: Modelling, Analysis, Verification and Certification, RSS Rail 2023, Berlin, Germany, 10 October - 12 October 2023 (pp. 62-77). Springer Science and Business Media Deutschland GmbH
Open this publication in new window or tab >>Remaining Useful Life Estimation for Railway Gearbox Bearings Using Machine Learning
2023 (English)In: Lecture Notes in Computer Science, Springer Science and Business Media Deutschland GmbH , 2023, p. 62-77Conference paper, Published paper (Refereed)
Abstract [en]

Gearbox bearing maintenance is one of the major overhaul cost items for railway electric propulsion systems. They are continuously exposed to challenging working conditions, which compromise their performance and reliability. Various maintenance strategies have been introduced over time to improve the operational efficiency of such components, while lowering the cost of their maintenance. One of these is predictive maintenance, which makes use of previous historical data to estimate a component’s remaining useful life (RUL). This paper introduces a machine learning-based method for calculating the RUL of railway gearbox bearings. The method uses unlabeled mechanical vibration signals from gearbox bearings to detect patterns of increased bearing wear and predict the component’s residual life span. We combined a data smoothing method, a change point algorithm to set thresholds, and regression models for prediction. The proposed method has been validated using real-world gearbox data provided by our industrial partner, Alstom Transport AB in Sweden. The results are promising, particularly with respect to the predicted failure time. Our model predicted the failure to occur on day 330, while the gearbox bearing’s actual lifespan was 337 days. The deviation of just 7 days is a significant result, since an earlier RUL prediction value is usually preferable to avoid unexpected failure during operations. Additionally, we plan to further enhance the prediction model by including more data representing failing bearing patterns.

Place, publisher, year, edition, pages
Springer Science and Business Media Deutschland GmbH, 2023
Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 14198 LNCS
Keywords
Gearbox bearing, Machine learning, Predictive maintenance, Railway, Remaining useful life, Bearings (machine parts), Forecasting, Gears, Maintenance, Railroads, Regression analysis, Vibrations (mechanical), Cost items, Electric propulsion systems, Life estimation, Lifespans, Machine-learning, Major overhauls, Remaining useful lives
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:mdh:diva-64606 (URN)10.1007/978-3-031-43366-5_4 (DOI)001156323700004 ()2-s2.0-85174442316 (Scopus ID)9783031433658 (ISBN)
Conference
5th International conference on Reliability, Safety and Security of Railway Systems: Modelling, Analysis, Verification and Certification, RSS Rail 2023, Berlin, Germany, 10 October - 12 October 2023
Available from: 2023-10-27 Created: 2023-10-27 Last updated: 2024-02-26Bibliographically approved
Bakhshi Valojerdi, Z., Rodriguez-Navas, G. & Hansson, H. (2022). Verifying the timing of a persistent storage for stateful fog applications. In: 6th International Conference on Computer, Software and Modeling (ICCSM): . Paper presented at 2022 6th International Conference on Computer, Software and Modeling (ICCSM) 21-23 July 2022 (pp. 1-8). Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>Verifying the timing of a persistent storage for stateful fog applications
2022 (English)In: 6th International Conference on Computer, Software and Modeling (ICCSM), Institute of Electrical and Electronics Engineers Inc. , 2022, p. 1-8Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, we analyze the failure semantics of a persistent fault-tolerant storage solution for stateful fog applications. This storage system is a container-based solution that provides data availability and consistency in a distributed container-based fog architecture. We evaluate the behavior of this storage system with a formal model that includes all the important time parameters and temporal aspects of the solution. This allows us to verify data consistency and other fault-tolerance properties of our system model while considering application startup latency, together with synchronization intervals and delays. We prove that the solution can tolerate failures at application, node, communication and storage level with the ability to automatically recover from failures and provides data consistency within the synchronization delay defined as t time units, which we can calculate for a given system configuration.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2022
Keywords
Containers; Digital storage; Fog; Fog computing; Semantics; Timing circuits, Data availability; Data consistency; Failure semantics; Fault-tolerant; Formal modeling; Persistent storage; Statefulness; Storage solutions; Storage systems; Time parameter, Fault tolerance
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-61645 (URN)10.1109/ICCSM57214.2022.00008 (DOI)2-s2.0-85146302832 (Scopus ID)
Conference
2022 6th International Conference on Computer, Software and Modeling (ICCSM) 21-23 July 2022
Available from: 2023-01-25 Created: 2023-01-25 Last updated: 2023-10-20Bibliographically approved
Bakhshi Valojerdi, Z., Rodriguez-Navas, G. & Hansson, H. (2021). Fault-tolerant Permanent Storage for Container-based Fog Architectures. In: Proceedings of the 2021 22nd IEEE International Conference on Industrial Technology (ICIT): . Paper presented at 2021 22ND IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT) (pp. 722-729).
Open this publication in new window or tab >>Fault-tolerant Permanent Storage for Container-based Fog Architectures
2021 (English)In: Proceedings of the 2021 22nd IEEE International Conference on Industrial Technology (ICIT), 2021, p. 722-729Conference paper, Published paper (Refereed)
Abstract [en]

Container-based architectures are widely used for cloud computing and can have an important role in the implementation of fog computing infrastructures. However, there are some crucial dependability aspects that must be addressed to make containerization suitable for critical fog applications, e.g., in automation and robotics. This paper discusses challenges in applying containerization at the fog layer and focuses on one of those challenges: provision of fault-tolerant permanent storage. The paper also presents a container-based fog architecture utilizing so-called storage containers, which combine built-in fault-tolerance mechanisms of containers with a distributed consensus protocol to achieve data consistency.

Series
IEEE International Conference on Industrial Technology, ISSN 2643-2978
Keywords
Kubernetes, ROS, Container, Orchestration, Cloud, Fog, Dependability, Fault-tolerance, Container Storage
National Category
Computer Engineering
Identifiers
urn:nbn:se:mdh:diva-53682 (URN)10.1109/ICIT46573.2021.9453473 (DOI)000687856000112 ()2-s2.0-85112532174 (Scopus ID)
Conference
2021 22ND IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT)
Available from: 2021-03-22 Created: 2021-03-22 Last updated: 2023-10-20Bibliographically approved
Bakhshi Valojerdi, Z. (2021). Persistent Fault-Tolerant Storage at the Fog Layer. (Licentiate dissertation). Västerås: Mälardalen University
Open this publication in new window or tab >>Persistent Fault-Tolerant Storage at the Fog Layer
2021 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Clouds are powerful computer centers that provide computing and storage facilities that can be remotely accessed. The flexibility and cost-efficiency offered by clouds have made them very popular for business and web applications. The use of clouds is now being extended to safety-critical applications such as factories. However, cloud services do not provide time predictability which creates a hassle for such time-sensitive applications. Moreover, delays in the data communication between clouds and the devices the clouds control are unpredictable. Therefore, to increase predictability an intermediate layer between devices and the cloud is introduced. This layer, the Fog layer, aims to provide computational resources closer to the edge of the network. However, the fog computing paradigm relies on resource-constrained nodes, creating new potential challenges in resource management, scalability, and reliability. Solutions such as lightweight virtualization technologies can be leveraged for solving the dichotomy between performance and reliability in fog computing. In this context, container-based virtualization is a key technology providing lightweight virtualization for cloud computing that can be applied in fog computing as well. Such container-based technologies provide fault tolerance mechanisms that improve the reliability and availability of application execution.  By the study of a robotic use-case, we have realized that persistent data storage for stateful applications at the fog layer is particularly important. In addition, we identified the need to enhance the current container orchestration solution to fit fog applications executing in container-based architectures. In this thesis, we identify open challenges in achieving dependable fog platforms. Among these, we focus particularly on scalable, lightweight virtualization, auto-recovery, and re-integration solutions after failures in fog applications and nodes. We implement a testbed to deploy our use-case on a container-based fog platform and investigate the fulfillment of key dependability requirements. We enhance the architecture and identify the lack of persistent storage for stateful applications as an important impediment for the execution of control applications. We propose a solution for persistent fault-tolerant storage at the fog layer, which dissociates storage from applications to reduce application load and separates the concern of distributed storage. Our solution includes a replicated data structure supported by a consensus protocol that ensures distributed data consistency and fault tolerance in case of node failures. Finally, we use the UPPAAL verification tool to model and verify the fault tolerance and consistency of our solution.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2021
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 309
Keywords
Dependability, Fog Computing, Fault-tolerance, Containerization
National Category
Embedded Systems Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:mdh:diva-55680 (URN)978-91-7485-518-0 (ISBN)
Presentation
2021-10-14, room Lambda, Mälardalens högskola, Västerås, 13:30 (English)
Opponent
Supervisors
Available from: 2021-08-31 Created: 2021-08-30 Last updated: 2021-09-23Bibliographically approved
Bakhshi Valojerdi, Z., Rodriguez-Navas, G. & Hansson, H. (2021). Using UPPAAL to Verify Recovery in a Fault-tolerant Mechanism Providing Persistent State at the Edge. In: 26th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2021: . Paper presented at 26th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2021Virtual, Vasteras7 September 2021 through 10 September 2021. Västerås: Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Using UPPAAL to Verify Recovery in a Fault-tolerant Mechanism Providing Persistent State at the Edge
2021 (English)In: 26th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2021, Västerås: Institute of Electrical and Electronics Engineers (IEEE), 2021Conference paper, Published paper (Refereed)
Abstract [en]

In our previous work we proposed a fault-tolerant persistent storage for container-based fog architecture. We leveraged the use of containerization to provide storage as a containerized application working along with other containers. As a fault-tolerance mechanism we introduced a replicated data structure and to solve consistency issue between the replicas distributed in the cluster of nodes, we used the RAFT consensus protocol. In this paper, we verify our proposed solution using the UPPAAL model checker. We explain how our solution is modeled in UPPAAL and present a formal verification of key properties related to persistent storage and data consistency between nodes.

Place, publisher, year, edition, pages
Västerås: Institute of Electrical and Electronics Engineers (IEEE), 2021
National Category
Computer Sciences Embedded Systems
Identifiers
urn:nbn:se:mdh:diva-55677 (URN)10.1109/ETFA45728.2021.9613178 (DOI)000766992600015 ()2-s2.0-85122923987 (Scopus ID)9781728129891 (ISBN)
Conference
26th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2021Virtual, Vasteras7 September 2021 through 10 September 2021
Available from: 2021-08-30 Created: 2021-08-30 Last updated: 2023-10-20Bibliographically approved
Bakhshi Valojerdi, Z. & Rodriguez-Navas, G. (2020). A preliminary roadmap for dependability research in fog computing. ACM SIGBED Review, 16(4), 14-19
Open this publication in new window or tab >>A preliminary roadmap for dependability research in fog computing
2020 (English)In: ACM SIGBED Review, E-ISSN 1551-3688, Vol. 16, no 4, p. 14-19Article in journal (Refereed) Published
Abstract [en]

Fog computing aims to support novel real-time applications by extending cloud resources to the network edge. This technology is highly heterogeneous and comprises a wide variety of devices interconnected through the so-called fog layer. Compared to traditional cloud infrastructure, fog presents more varied reliability challenges, due to its constrained resources and mobility of nodes. This paper summarizes current research efforts on fault tolerance and dependability in fog computing and identifies less investigated open problems, which constitute interesting research directions to make fogs more dependable. 

Place, publisher, year, edition, pages
Association for Computing Machinery, 2020
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-46794 (URN)10.1145/3378408.3378410 (DOI)2-s2.0-85077810723 (Scopus ID)
Available from: 2020-01-23 Created: 2020-01-23 Last updated: 2022-04-22Bibliographically approved
Samizadeh Nikoui, T., Balador, A., Rahmani, A. M. & Bakhshi, Z. (2020). Cost-Aware Task Scheduling in Fog-Cloud Environment. In: : . Paper presented at 2020 CSI/CPSSI International Symposium on Real-Time and Embedded Systems and Technologies (RTEST).
Open this publication in new window or tab >>Cost-Aware Task Scheduling in Fog-Cloud Environment
2020 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Cloud computing provides computing and storage resources over the Internet to provide services for different industries. However, delay-sensitive applications like smart health and city applications now require computation over large amounts of data transferred to centralized cloud data centers which leads to drop in performance of such systems. The new paradigms of fog and edge computing provide new solutions by bringing resources closer to the user and provide low latency and energy efficiency compared to cloud services. It is important to find optimal placement of services and resources in the three-tier IoT to achieve improved cost and resource efficiency, higher QoS, and higher level of security and privacy. In this paper, we propose a cost-aware genetic-based (CAG) task scheduling algorithm for fog-cloud environments, which improves the cost efficiency in real-time applications with hard deadlines …

National Category
Engineering and Technology Computer Systems
Identifiers
urn:nbn:se:mdh:diva-50985 (URN)10.1109/RTEST49666.2020.9140118 (DOI)2-s2.0-85089567483 (Scopus ID)978-1-7281-7551-5 (ISBN)
Conference
2020 CSI/CPSSI International Symposium on Real-Time and Embedded Systems and Technologies (RTEST)
Available from: 2020-10-01 Created: 2020-10-01 Last updated: 2020-11-16Bibliographically approved
Salman Shaik, M., Struhar, V., Bakhshi Valojerdi, Z., Dao, V.-L., Desai, N., Papadopoulos, A., . . . Venito, A. (2020). Enabling Fog-based Industrial Robotics Systems. In: The 25th International Conference on Emerging Technologies and Factory Automation ETFA2020: . Paper presented at The 25th International Conference on Emerging Technologies and Factory Automation ETFA2020, 08 Sep 2020, Vienna, Austria.
Open this publication in new window or tab >>Enabling Fog-based Industrial Robotics Systems
Show others...
2020 (English)In: The 25th International Conference on Emerging Technologies and Factory Automation ETFA2020, 2020Conference paper, Published paper (Refereed)
Abstract [en]

Low latency and on demand resource availability enable fog computing to host industrial applications in a cloud like manner. One industrial domain which stands to benefit from the advantages of fog computing is robotics. However, the challenges in developing and implementing a fog-based robotic system are manifold. To illustrate this, in this paper we discuss a system involving robots and robot cells at a factory level, and then highlight the main building blocks necessary for achieving such functionality in a fog-based system. Further, we elaborate on the challenges in implementing such an architecture, with emphasis on resource virtualization, memory interference management, real-time communication and the system scalability, dependability and safety. We then discuss the challenges from a system perspective where all these aspects are interrelated.

National Category
Engineering and Technology Computer Systems
Identifiers
urn:nbn:se:mdh:diva-51699 (URN)10.1109/ETFA46521.2020.9211887 (DOI)000627406500007 ()2-s2.0-85093363908 (Scopus ID)978-1-7281-8956-7 (ISBN)
Conference
The 25th International Conference on Emerging Technologies and Factory Automation ETFA2020, 08 Sep 2020, Vienna, Austria
Projects
FORA - Fog Computing for Robotics and Industrial Automation
Available from: 2020-10-20 Created: 2020-10-20 Last updated: 2022-11-08Bibliographically approved
Organisations

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