Theses and Dissertations

Permanent URI for this collectionhttp://ir.daiict.ac.in/handle/123456789/1

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Open Access
On heterogeneous distributed storage systems: bounds and code constructions
(Dhirubhai Ambani Institute of Information and Communication Technology, 2019) Gopal, Krishna; Manish K. Gupta
In Distributed Storage Systems (DSSs), usually, data is stored using encoded packets on different chunk servers. In this thesis, we have considered heterogeneous DSSs in which each node may store a different number of packets and each having different repair bandwidth. In particular, a data collector can reconstruct the file at time t using some specific nodes in the system, and for arbitrary node failure, the system can be repaired by some set of arbitrary nodes. Using min-cut bound, we investigate the fundamental trade-off between storage and repair cost for our model of heterogeneous DSS. In particular, the problem is formulated as a biobjective optimization linear programming problem. For an arbitrary DSS, it is shown that the calculated min-cut bound is tight. For a DSS with symmetric parameters, a well known class of Distributed Replication-based Simple Storage (DRESS) codes is Fractional Repetition (FR) code. In such systems, the replicas of data packets encoded by Maximum Distance Separable (MDS) code, are stored on distributed nodes. Most of the available constructions for the FR codes are based on combinatorial designs and Graph theory. In this thesis, FR codes with generalized parameters (such as replication factor of each packet are not same and storage capacity of each node are also not same) are considered, and it is called as Generalized Fractional Repetition (GFR) code. For the GFR code, we propose an elegant sequence-based approach for the construction of the GFR code called Flower codes. Further, it is shown that any GFR code is equivalent to a Flower code. The condition for the universally good GFR code is given on such sequences. For some sequences, the universally good GFR codes are explored. In general, for the GFR codes with non-uniform parameters, bounds on the GFR code rate and DSS code rate are studied. Further, we have shown that a GFR code corresponds to a hypergraph. Using the correspondence, properties and bounds of a hypergraph are directly mapped to the associated GFR code. In general, necessary and sufficient conditions for the existence of a GFR code is obtained using the correspondence. It is also shown that any GFR code associated with a linear hypergraph is universally good.
Open Access
Policy based resource allocation on infrastructure as a service cloud
(Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Vora, Dhairya; Chaudhary, Sanjay; Bise, Minal
Cloud computing refers to the provision of computational resources on demand. Resource allocation is an important aspect in cloud computing. Cloud user asks for resources in terms of a lease. Lease stores the information about required resources and the time at which these resources are required. Cloud provider accepts the lease if it can provide guarantee for assigning resources at asked time to the cloud user. Better scheduling algorithm can accept more number of leases and hence give better resource utilization. Cloud provides four types of leases: immediate, advance reservation, best effort and deadline sensitive. Immediate allocation policy accepts the lease if resources are available, else it rejects the lease. Advance reservation policy accepts the lease if resources are available at the asked time, else it rejects the lease. Best effort allocation policy accepts the lease as soon as the resources are available. Deadline sensitive leases have parameters like required resources, startTime, endTime and duration. Scheduler can accept such lease by providing required resources for the asked duration of time between given startTime and endTime. Haizea is a resource lease manager which handles the scheduling of the lease. Proposed algorithm extends the current scheduling algorithm of Haizea for deadline sensitive type of leases. Aim of the thesis is to improve resource utilization by extending the current scheduling algorithms of Haizea. Proposed scheduling algorithm accepts more number of leases by dividing a deadline sensitive lease into multiple slots and by back filling already.
Open Access
Migration of database from one cloud to other clouds
(Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Bhatt, Shreyansh; Chaudhary, Sanjay
On demand services and scalability features of cloud computing has attracted many customers to move their applications into cloud. Cloud service providers are following di erent standards to host applications and data. Data must be stored according the schema of a particular cloud service provider. A need can arise to migrate cloud application and/or data to another cloud service provider. In that case, the relevant code, and structure of database must be modi ed based on newly identi ed cloud service provider. Which is a costly deal and as a consequence, chang ing cloud service provider becomes di cult. This issue is regarded as vendor lock-in in terms of cloud computing. Current study will help to identify issues of migrating database between two clouds and development of novel techniques, which would facilitate this migration. For this, RDF /RDFS (Resource Description Framework/Resource Description Framework Schema) is used as an intermediate model. Automation in migration process is achieved by transformation algorithms. Bigtable, Google App Engine datastore, is taken as a cloud datastore and algorithms are developed and implemented to convert RDF/RDFS data into data that can be stored in Bigtable and vice versa. Results are shown for the same. Subsequently, the same algorithm is generalized to store RDF/RDFS data into any cloud datastore.
Open Access
Resource allocation on infrastructure as a service cloud using policies
(Dhirubhai Ambani Institute of Information and Communication Technology, 2010) Nathani, Amit; Divakaran, Srikrishnan
Conventionally, a cloud refers to an Infrastructure as a service cloud. Infrastructure as a service cloud providers manage a large set of computing resources. These resources can be provided to cloud users on demand in the form of virtual machines. Cloud consumers do not need to manage resources and be worried about the performance issues because they are handled by cloud providers. Resource allocation in the context of infrastructure as a service cloud means allocating virtual resources namely computing capacity, storage etc. to competing requests based on pre-defined resource allocation policies. In real world most of the Infrastructure as a service clouds rely on simple resource allocation policies like immediate and best effort. Immediate means the resources are allocated if they are available or the request is rejected and best effort means the requested resources are allocated if they are available or the request is placed in first come first serve queue. Sometimes it is not possible for a cloud provider to satisfy all the requests which come to them immediately because of lack of resources. In this case cloud providers can benefit from more complex resource allocation policies. Haizea is a resource lease manager that tries to address above issues. It uses resource leases as resource allocation abstraction and implements these leases as virtual machines. Currently, it supports four kinds of resource allocation policies: immediate, best-effort, advance reservation and deadline sensitive. The aim of thesis is to extend the current scheduling algorithm of Haizea to support deadline leases in an efficient manner. A dynamic planning based scheduling algorithm is proposed which will admit new leases and prepare the schedule whenever a new lease can be accommodated. The proposed algorithm is implemented in Haizea. Experiments are performed to demonstrate the effectiveness of it. The results show that it maximizes resource utilization and acceptance of leases compared to the existing algorithm of Haizea.
Open Access
Negotiation for resource allocation on infrastructure as a service cloud
(Dhirubhai Ambani Institute of Information and Communication Technology, 2010) Akhani, Janki; Divakaran, Srikrishnan
The Cloud is a computing platform that provides dynamic resource pools, virtualization, and high availability. Cloud computing infrastructures can allow enterprises to achieve more efficient use of their IT hardware and software investments. Infrastructure As A Service (IAAS) cloud providers manage a large set of computing resources. These resources can be provided to cloud consumers on demand in the form of virtual machines. Cloud consumers do not need to manage resources and be worried about the performance issues because they are handled by cloud providers. Open Nebula is an open source cloud toolkit which can be used to setup an IAAS cloud. It has three components: Open Nebula Core, Virtual Machine Scheduler and Cloud Drivers. Haizea is an open-source resource lease manager, and can act as a virtual machine scheduler for Open Nebula or used on its own as a simulator to evaluate the performance of different scheduling strategies. Haizea supports four kinds of resource allocation policies: immediate, best-effort, advance reservation and deadline sensitive. To reserve resources in advance using Haizea, consumer submits parameters like amount of resources, start time and duration of a reservation as a request. If one or more parameters can not be satisfied, then Haizea will reject the request. This method is very rigid method because it does not allow negotiation of any parameter. Consumer can resubmit new requests by modifying previously submitted request parameters. Consumer will not be aware of the current resource allocation on provider side so, the chances of new requests getting rejected are more. Thus, it will increase communication overhead between cloud provider and consumer as well as it will decrease resource utilization on provider’s side. It will also degrade the performance of a provider in managing many incoming requests due to previously rejected ones. To overcome the above problems, negotiation can be provided. Negotiation process consists of three components which are negotiation protocol, negotiation objectives and agents’ decision making algorithm. The proposed algorithm to generate set of counter offers is a part of decision making model at provider side. It provides set of counter offers to consumer when his advance reservation request gets rejected. It provides set of counter offers considering parameters’ flexibilities to maximize the chances of their acceptance. The proposed algorithm for User selection policy is a part of decision making model at consumer side. Consumer can get best suitable offer from set of counter offers using the algorithm of user selection policy. Ranking algorithm is a partof algorithm for user selection policy. Using this ranking algorithm, consumers will get suitable offers sorted according to their needs. It will reduce consumers’ efforts to go through all the provided counter offers and choose best suitable one. These algorithms are implemented in Haizea. Experiments are performed to demonstrate the effectiveness of algorithms. The results show that the proposed algorithm to generate counter offers maximizes resource utilization and acceptance of requests compared to rigid and exact methods.
Open Access
Bidirectional service composition
(Dhirubhai Ambani Institute of Information and Communication Technology, 2010) Khakhkhar, Sandip; Chaudhary, Sanjay
Service is a network addressable software component to perform a specific task. A service consumes given input parameters, performs specific task based on input parameters and returns the result in terms of output parameters. A service request specifies required task in terms of input parameters that can be provided and output parameters that are required. A service discovery mechanism can be used to find services that can be executed to satisfy service request. Service and service request is match by comparing their input/output parameters. A service request may be complex enough that it can not be satisfied by an individual service. It might be possible to execute a chain of services in a particular order to satisfy service request. This chain of services is referred as composition plan and service offered by executing this composition plan is referred as composite service. The aim of service composition algorithm is to generate a composition plan and generate composite service to satisfy service request. Services involved in composition plan are selected manually while designing composite service in static composition process. This process consumes considerable amount of time and effort. It is also vulnerable to changes in input/output of services. A dynamic composition algorithm is required that can automatically select services involved in composite plan and generate a composite service on-the-fly. Main issue with dynamic composition algorithms is composition time taken by algorithm to generate a composite service. Composition time indicates duration of the time at which the service request was submitted to the algorithm till the algorithm generate a composite service that can satisfy service request. Composition time depends upon the number of services required to explore in order to find services that can take part in composite plan. Dynamic composition algorithms presented in previous work mainly follows either forward chaining approach or backward chaining approach to find a composite service. Performance of algorithms based on forward chaining approach or backward chaining approach suffers for certain cases to generate a composite service where number of services explored increases exponentially as number of iterations increases. This work proposes a dynamic composition algorithm that gives consistent performance across all the cases. Proposed algorithm approaches from two directions alternatively, one follows forward chaining approach and other follows backward chaining approach. Composition algorithm following only forward chaining approach or backward chaining approach performs all the iterations in one direction only where as proposed algorithm requires only half number of iterations in both directions. Algorithm uses two types of matching strategy to compare input/output parameters. First one is based on keyword matching and second one based on semantic matching strategy. Performance of proposed algorithm is evaluated by performing relevant experiments and results are compared with algorithms based on only forward chaining approach or backward chaining approach. Proposed algorithm explores less number of services and takes less composition time compared to algorithms based on only forward chaining approach or backward chaining approach.
Open Access
Scheduling and isolation in virtualization
(Dhirubhai Ambani Institute of Information and Communication Technology, 2009) Somani, Gaurav; Chaudhary, Sanjay
Virtual machine (VM) based server implementation is popular for numerous advantages like fault isolation, efficient hardware utilization, security and ease of management. Virtual machine monitor (VMM) like Xen is a popular virtualization software to manage virtual machines by scheduling them to use resources such as CPU, memory and network. Performance isolation is desirable in virtual machine based infrastructures to meet Service Level Objectives (SLO). In performance isolation, no virtual machine should affect performance of other co hosted virtual machine, which shares the same hardware. Virtual machine schedulers are the key operators in allocating resources among virtual machines. This requires special attention towards scheduling as fairness and resource isolation are the key requirements for which any user virtualizes servers. I/O models are the main bottlenecks in sharing resources among virtual machines. To evaluate isolation property, we need to analyze resource sharing and utilization among virtual machines.
The thesis aims to evaluate the performance isolation achieved by Xen in different scheduler configurations. Experiments are performed using different resource intensive applications to get an insight into isolation. These tests include CPU, Network and Disk I/O intensive benchmarks. Considering the equal importance of I/O applications in virtualized environment, tests for interactive applications in conjunction with CPU intensive applications are also performed. Experiment results show that Isolation is critical when we run I/O application in conjunction with CPU intensive applications. But effective parameter and scheduler configuration can lead towards better isolation as well as utilization. Global balancing of load across all the available physical processors in a physical machine is important characteristic of a scheduler. Xen’s Credit scheduler aims to achieve global load balancing on multiprocessor systems. Xen’s Simple Earliest Deadline First (SEDF) scheduler can not be used in production environment due to unavailability of this important feature of load balancing. Many applications requires scheduler like SEDF in their implementation to fulfill the requirement of interactive applications. This thesis investigates requirements of this feature and discusses algorithmic design and implementation of a developed user space load balancing program. Experiments show a balance among number of physical processors with better utilization of
Open Access
Dynamic information management methodology with situation awareness capability
(Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Sorathia, Vikram; Chaudhary, Sanjay; Maitra, Anutosh
In present world, information generation, handling and utilization is deeply integrated with various activities. From entertainment to serious professional activities, information content is managed in some ways. Appropriate information content is beneficial and sometimes becomes critical to life, business or the environment that supports them. Handling of information is therefore increasingly perceived as integral part of the activities. Systematic approach for handling information by individuals and organization is known as “information management”. A common approach towards information management is limited to recording and retrieval of data pertinent to various human activities or environmental processes. The resulting system acts as a computerized log of human activity transactions or phenomena recorded in natural environment. Systems supporting information management are defined based on project specific requirements with limited scope. The project-oriented or mission-specific engineering approaches employed in designing such systems also restrict the scope of supported information management activities. It is important to realize that projects or missions are identified only as short-term objective that contribute to the long-term goals and vision of entities. A system defined to serve shortterm goals may soon become incapable of meeting the emergent needs. Even with accurate estimation of potential change, external intervention cannot be avoided due to dependence of knowledge, authority and resource capability required to realize the goals. The dynamism exhibited by relevant entities, results in continuous change of needs resulting in constantly changing requirements. With increasing amount of complex interdependence and dynamic behavior of relevant entities, the task of information management has become difficult. From the scale of effort required to address the complex interdependence, it is realized that information management cannot be carried out with systems created and managed by individuals and organizations in isolation. Also, from the dynamic behavior and evolution exhibited by relevant entities, it is realized that underlying systems must also undergo change at similar rates. In summary, a paradigm shift is required in information management strategy and information should be made available as critical infrastructure service. This thesis argues that information management should be based on the goals of the involved individuals instead of the conventional activity-oriented approaches. The required approach not only should support the goal-specific information, but also allow identification of newer goals with emerging trends in the system. Information need of individuals and organizations is vi uniquely identified in the form of situations. The state of having access to relevant information is defined as situation awareness capability. The situation awareness approach proposed for information management strategy identifies role of individuals in producing and consuming information. It is based on the realization that, no one can have the global picture of the situation, but can play a role in building the rich picture of situation by contributing the part of the situation known. The resulting coordinated effort allows realization of situation awareness capability to the contributors. In order to support the argument, the situation theory and semantics is accepted as base. It is stated that small coordinated assertions regarding situations can be integrated to prepare a rich representation of the world. Qualitative and quantitative estimate of information needs are identified based on the commitment towards goals. Three problems are identified in identification of information needs of individuals and organizations. The implied goal-matching problem relates to the challenge of identification and handling of goals that are not explicitly expressed. The transient system element problem indicates the challenges of numerous short-lived entities that are relevant to the information needs. The third problem is regarding identification of the event space, a set of all possible events that are possible in given scenario. As a solution to this problem, a conceptual modeling strategy followed by information processing strategy is proposed. The proposal utilizes the rich representation created with conceptual modeling process in meeting the information needs. It is established that scale and scope of work involved in conceptual modeling and information processing requires large-scale collaboration from various stakeholders. For consistency of collaborative effort, appropriate method content is provided. Reuse and traceability of work products are encouraged with unique situation awareness artifacts furnishing information about task and availability of reusable outcomes and other related information. The proposed information management facility is prescribed as a critical infrastructure service required in achieving the large-scale collaboration. Appropriate system architecture is introduced to facilitate realization of required domain specific middleware services.
Open Access
Web services policy in grid
(Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Desai, Amee Anilbhai; Chaudhary, Sanjay
Service-oriented computing enables service providers to publish their business functionalities in the form of abstract contracts, which can be discovered by service consumers based on open and standard protocols. Enterprise may be running a number of multiple business processes in parallel, which may require different services to fulfil the functionality. There are number of factors that both service provider and service consumer should consider before they interact with each other. Web services standards are used for acquiring interoperability among services for large scale adoption of architecture. In Web service selection phase without the use of policy, a service consumer selects the Web service which matches the functional requirements. For satisfying non-functional requirements of a service consumer, policy is used in Web service selection phase. This thesis proposes an approach and architecture to select Web services based on WS-Policy in grid. Service selection depends on metadata and policy. There is a need for dynamic selection services based on runtime environment such as content (semantics), and contract (policy). This thesis proposes an approach and architecture for dynamic selection of services based on policy and semantic .To provide better search, query, composition, and management, there is a need for mechanism to group these services based on the requirements of clients and business processes. This thesis proposes context and location based approach for service grouping and group notification. Context and location provide powerful mechanism for the better search, query, grouping and group notification to the services, and it allows customization based on user preferences, role, and location to improve personalization. The thesis proposes context and location driven grid business process to aggregate information from multiple sources according to the preferences of clients. A policy based service grouping approach is used to aggregate services. For achieving location driven approach, this thesis develops virtual organization and for specifying preferences in virtual organization, a policy is used.

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