PONE-D-24-01820E2SVM: Electricity-Efficient SLA-aware Virtual Machine Consolidation Approach in Cloud Data CentersPLOS ONE

Dear Dr. Aqeel,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Apr 12 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Jacopo Soldani

Academic Editor

PLOS ONE

Journal requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. Please note that PLOS ONE has specific guidelines on code sharing for submissions in which author-generated code underpins the findings in the manuscript. In these cases, all author-generated code must be made available without restrictions upon publication of the work. Please review our guidelines at https://journals.plos.org/plosone/s/materials-and-software-sharing#loc-sharing-code and ensure that your code is shared in a way that follows best practice and facilitates reproducibility and reuse.

3. Thank you for stating the following financial disclosure:

“The authors extend their appreciation to the Deputyship for Research& Innovation, Ministry of Education in Saudi Arabia, for funding this research work through the project number ISP-2024.”

Please state what role the funders took in the study.  If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript."

If this statement is not correct you must amend it as needed.

Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf.

4. Thank you for stating the following in the Acknowledgments Section of your manuscript:

“The authors extend their appreciation to the Deputyship for Research& Innovation, Ministry of Education in Saudi Arabia, for funding this research work through the project number ISP-2024.”

We note that you have provided funding information that is currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form.

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

“The authors extend their appreciation to the Deputyship for Research& Innovation, Ministry of Education in Saudi Arabia, for funding this research work through the project number ISP-2024.”

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: I Don't Know

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: To reduce energy consumption and SLA violations, the authors propose a VM consolidation algorithm. The experimental results illustrate that the proposed algorithm performs better than other algorithms in terms of energy consumption and SLA violations. However, the following problem should be addressed:

(1)The Abstract of this paper should be rewritten.

(2) In the paper, what is the time complexity for the proposed algorithm? It is better for the authors to give more explanations of the algorithms, such as the function of each step, and the overall basic idea.

(3)The authors make a comparison with other algorithms in the paper. However, these algorithms are out of date. It is not fair to make a comparison with these algorithms. Could the authors make a comparison with the newly published algorithms in the field of VM deployment, e.g., “An Energy-efficient VM Allocation Algorithm for IoT Applications in a Cloud Data Center”, 2021 (The source code and videos are shared on GitHub https://github.com/mshojafar/sourcecodes/tree/master/Zhou2021AFED-EF_Sourcecode); and “Minimizing SLA Violation and Power Consumption in Cloud Data Centers Using Adaptive Energy-aware Algorithms”.

(4)For the comparison algorithms, It is suggested to make a simple introduction in the experiment part.

(5) The quality of the Figures in the paper should be further improved in the revision.

(6) In the paper, the authors evaluate the energy consumption. However, any power model is essential for energy-aware algorithms. Have the authors considered selecting other energy consumption models? The author can benefit from these references to enrich these parts, such as “IECL: An Intelligence Energy Consumption Model for Cloud Manufacturing”, DOI: 10. 1109/TII. 2022.3165085; doi:10.1109/TGCN.2021.3121961; DOI: 10.1007/s00521-019-04119-7.

(7) There are many spelling errors in the manuscript. A thorough spelling check is required in the revision.

Reviewer #2: This paper proposes an approach to improve Virtual Machines (VMs) consolidation in a data center by balancing Service Level Agreement (SLA) violations and energy consumption. The approach is based on a multi-objective consolidation architecture that individuates under-utilised servers to be put in low power mode and over-utilised servers to migrate VMs in order to avoid performance degradation which could lead to SLA violations.

The devised algorithms are evaluated by simulation and compared with existing VM migration policies.

The topics of the paper are interesting and with growing importance in the last few years. The paper has a standard structure and, generally, is well-written with only some typos and small spelling mistakes.

Given that energy consumption is a central topic of the paper, I think the energy model should be motivated and explained better to convince the reader that energy consumption is linearly proportional to CPU utilisation. The cited energy model refers to a study from 2007 and I believe that data center technologies are changed in the meantime. Moreover, my intuition is that such linear relation is referred to CPU-bound applications only, and I do not know if can be considered for the general case. I suggest studying and discussing these points in the paper.

Moreover, I think that the used algorithm's execution should be evaluated in terms of energy consumption since the result of about 9% energy consumption in the evaluation section could be decreased by the algorithms. E.g. if the algorithms execution consumes 10% of the overall energy there is no gain in terms of energy consumption.

Furthermore, I suggest evaluating if unutilised servers can be automatically shut down to reduce energy consumption and if the power-up when they are needed is feasible in terms of time to avoid SLA violations.

In conclusion, I think that the paper can be improved but could be accepted after revision of some parts.

Reviewer #3: In this paper, the authors proposed an Energy-Efficient Service Level Agreement (SLA)-‎aware Virtual Machine (E2SVM) to control energy consumption through optimization of ‎existing resources. Overall, the paper is well organized and written in a rigorous and clear ‎style. The current article necessitates a comprehensive structural revision to enhance its ‎coherence. Please revise the following issues:‎

‎-‎ Although the ABSTRACT structure is good, I suggest that the philosophy of using the ‎proposed method should be explained.‎

‎-‎ In my opinion, the INTRODUCTION section needs to be revised. In this section there ‎should be three points: 1) motivation, 2) a summary of the challenges of previous ‎studies, and 3) contribution.‎

‎-‎ The Related Work section is too short, should have additional resources, and may be ‎separated by subjects: QoS, Energy consumption, and SLA, subjects related to the ‎article. Here are some suggestions: " Server ‎Consolidation Algorithms for Cloud ‎Computing: Taxonomies and Systematic Analysis of ‎Literature", “MECpVmS: an SLA ‎aware energy-efficient virtual machine selection policy for green cloud computing”, " ‎Reducing Energy Footprint in Cloud Computing: A Study on the Impact of ‎Clustering ‎Techniques and Scheduling Algorithms for Scientific Workflows", “Power and thermal-‎aware virtual machine scheduling optimization in cloud data center”, "Computing ‎‎Resources Scalability Performance Analysis in Cloud Computing Data Center", ‎‎"HEPGA: a ‎new effective hybrid ‎algorithm for scientific workflow scheduling in cloud ‎computing ‎environment", "Modeling and analysis of quality of service and energy ‎consumption in cloud environment”. ‎

‎-‎ The authors stated in the abstract “So, this approach can be used in real-world data ‎centers through minimizing of energy wastage thereby maintaining low SLA violations ‎or fluctuations”, but no real implementation was made in the paper. While the ‎experiment and results presented are intriguing and indicative of promise, it is ‎imperative to validate these outcomes through real-world application. I recommend the ‎incorporation of empirical experiments to facilitate a meaningful comparison with ‎simulation results; it is better to analyze the time complexity of the proposed method in ‎the worst case.‎

‎-‎ While the article alludes to cost reduction associated with Cloud services, a ‎comprehensive examination of this aspect remains elusive. It would be prudent for the ‎author to expound upon the topic, particularly focusing on unreliable services like ‎preemptible servers (e.g., Spot Instances on Amazon and Preemptible instances on ‎Google). Noteworthy articles like "MULTS: A Multi-cloud Fault-tolerant Architecture to ‎Manage Transient Servers in Cloud Computing" (Journal of Systems Architecture, 2019) ‎and "Portfolio-driven Resource Management for Transient Cloud Servers" (ACM on ‎Measurement and Analysis of Computing Systems 2019) are worth considering. The ‎viability of unreliable services could be assessed within the framework of Fault ‎Tolerance approaches, thereby underlining the potential trade-offs in terms of Quality of ‎Service (QoS). In light of these considerations, the article's focus may be refined to ‎address these intricate aspects;‎

‎-‎ The main limitation of the proposed methods should be explained in detail;‎ ‎

‎-‎ The contribution and novelty of this work should be further justified and future studies ‎‎should be given;‎ ‎

‎-‎ The simulation environment should be provided in detail, e.g., software, sampling size, ‎solver ‎type, etc.‎

‎-‎ An important point needs to be included in this article: the type of application that can ‎be executed using the proposed model. The inclusion of this facet would enrich the ‎article's scope and applicability;‎

‎-‎ There are still some grammatical errors in the manuscript. Authors should use software ‎such as Grammarly for proof-checking. ‎

‎-‎ The tense of the verbs in the CONCLUSION section must be past tense. In this section, ‎the most important numerical improvements of the proposed method should be ‎mentioned and marginal explanations should be avoided. In addition, the suggestions ‎mentioned for further research should be well presented.‎

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: ZHOU ZHOU

Reviewer #2: No

Reviewer #3: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

E2SVM: Electricity-Efficient SLA-aware Virtual Machine Consolidation Approach in Cloud Data Centers

PONE-D-24-01820R1

Dear Dr. Aqeel,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Jacopo Soldani

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: All of my concerns have been addressed (including the experiment part and other parts). It is suggested that you accept this paper.

Reviewer #2: (No Response)

Reviewer #3: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Zhou Zhou

Reviewer #2: No

Reviewer #3: No

**********