I am an Assistant Professor in the School of Computer Science at McGill University, where I lead the Data-Intensive Storage and Computer Systems Laboratory (DISCS Lab). My current focus is on storage and persistent memory technologies, with an emphasis on the way we manage large-scale data for emerging workloads in Data Science, Data Analytics, and the Edge Computing.
I completed my PhD in Computer Science at the University of Sydney in 2020, advised by Prof. Willy Zwaenepoel. My dissertation research was on the design and implementation of efficient key-value stores for future hardware and performance requirements. My PhD was generously supported by The University of Sydney Faculty of Engineering and IT Dean's Postgraduate Research Scholarship and by the EPFL Fellowship for Doctoral Studies. I have earned my Bachelors and Masters degrees in Computer Science from EPFL.
Office: McConnell 113N
I have open positions for PhD students! These positions are fully funded. I also welcome McGill Masters and Undergraduate students for research projects. Interested in groundbreaking computer systems research? Have a look at the research focus areas and get in touch if you are motivated, have a strong academic record, and you'd like to join the team! Please read this before sending me email.
The McGill CS Systems Seminar will restart in Fall '21. Undergraduate and graduate student speakers are welcome! Please get in touch if you have suggestions for great speakers or if you'd like to subscribe to our mailing list.
[Jun. 2021] I was awarded a John R. Evans Leaders Fund (JELF) Grant by the Canada Foundation for Innovation. Thank you, CFI!
[Jun. 2021] I was awarded a Discovery Grant by the Natural Sciences and Engineering Research Council of Canada. Thank you, NSERC!
[Apr. 2021] I will be giving a seminar on the challenges of zettabyte-scale real-time data management in the University of Melbourne CIS Series.
[Apr. 2021] Congratulations to Yunjia Zheng for winning the McGill School of Computer Science Feng Qian Award for Undergraduate Research!
[Mar. 2021] Congratulations to Brian Hu for winning the NSERC Undergraduate Research Award!!
[Feb. 2021] I will give a keynote speech at the Australasian Computer Science Week (ACSW 21)
[Dec. 2020] I will co-teach COMP-310/ECSE-427 Operating Systems together with Prof. Joseph Vybihal in the winter semester of 2021.
[Oct. 2020] My doctoral dissertation was awarded the CORE John Makepeace Bennett Award 2021! Many thanks to the CORE committee for selecting my thesis as the winner, my advisor Prof. Willy Zwaenepoel, and Prof. Irena Koprinska from the University of Sydney for supporting my application and encouraging me to apply, and to Dr. Ricardo Bianchini, Prof. Vijay Chidambaram, and Prof. Frans Kaashoek for reviewing my thesis.
[Aug. 2020] I will serve in the SOSP '21, EuroSys '21 and SIGMOD '21 PCs, and the OSDI '21 ERC.
[Aug. 2020] My Doctoral Dissertation has been nominated by the University of Sydney for this year's CORE John Makepeace Bennett Award, for the best Computer Science dissertation in Australia and New Zealand. Each department can nominate one thesis each year. Big thanks to my advisor, Willy Zwaenepoel, for his support and guidance!
[Aug. 2020] I will give a talk at the Roundtable on future of data management systems, organized by the University of Waterloo.
Current Research Focus
Data powers everything we do and we are collecting it at unprecedented rates. The driver for my current research is to create a storage infrastructure that enables us to gain insights from this data in a fast and energy-conscious manner. I am particularly interested in the following areas:
Storage Systems for Data Science
Data Science and AI workloads are ubiquitous. From taking care of our health, to running businesses, to managing our energy systems and transport planning, we leverage data science and learning to make more informed decisions. We are able to obtain these insights through the combination of smart algorithms and access to vast amounts of data. Data management now poses a bottleneck that can unfortunately slow down the entire pipeline. The way data is stored and accessed strongly influences how fast the algorithms can provide us with useful insights.
Research Direction: The needs of Data Science workloads are poorly met by current general-purpose storage systems. Consequently, to obtain fast results systems rely on heuristics, approximations, or use of stale information. I am interested in designing and building a new storage system that (1) scales with the vast datasets used by Data Science workloads, (2) ingests and cleans new incoming data at high throughput, (3) serves data with low latency, and (4) is energy-efficient. This challenging goal entails many research directions, such as identifying opportunities to reduce data movement, designing adaptable data structures that harmonize with Data Science workloads, and the creative use of new storage resources (e.g., NVRAM, fast SSDs, etc.).
Contact me for more details.
Data Management for the Internet of Things
The Internet of Things (IoT) is a fast growing field which produces vast amounts of data. In fact, it is estimated that the data produced by IoT workloads alone in 2025 will be larger than all of the data we will produce in 2020. Naturally, this is an excellent opportunity for storage research.
Research Direction: From a storage systems perspective, IoT workloads pose serious challenges in terms of resource management. Numerous IoT settings make use of battery-powered devices with limited energy, low storage and data processing capacities, and unreliable connectivity. An interesting direction is determining at what granularity such systems should store data at the sensor-, edge-, and cloud-levels, while developing energy-efficient schemes for data-filtering and data-movement between these layers. In addition, the nature of the collected IoT data raises compelling questions as well. One possible avenue is designing data layouts that are suitable for storing vast amounts of noisy data, which may also contain high levels of redundancy (e.g., in video surveillance systems).
Contact me for more details.
Reimagining Storage Building Blocks for Fast Devices
Emerging storage technologies challenge fundamental assumptions in computer systems design. One major assumption being challenged is the significant performance gap between memory and persistent storage access. This gap is now bridged by Byte-addressable persistent memory (e.g., Intel 3D XPoint). Another assumption is that I/O bandwidth is the main bottleneck in storage systems. This too has changed with the development of new fast drives (e.g., Intel Optane NVMe SSDs) shifting the bottleneck to the CPU. In addition, the storage stack is getting deeper and more heterogeneous. It is likely that in a typical server developers and system administrators will have to manage RAM, persistent memory, different types of SSDs and hard disks.
Research Direction: These hardware advances provide an opportunity to redesign the basic storage building blocks, such as file systems, caching policies, key-value stores, and relational databases, as well as re-questioning the appropriate level of support that should be ensured by the Operating System. Ultimately, given that the hardware and the workloads keep evolving, my long-term vision is to create a framework that automatically generates storage systems which meet the desired performance requirements, given the workload profile and a set of generic hardware characteristics (e.g., sequential access speed relative to the random access speed, bandwidth, storage capacity etc.) as inputs.
Contact me for more details.
Key-value stores (KVs) are a crucial component in cloud computing because they can efficiently handle large-scale, diverse data (e.g., deployed in the infrastructure of Google, Apple, Facebook, and Amazon). In my dissertation, Redesigning Persistent Key-Value Stores for Future Workloads, Hardware, and Performance Requirements, I proposed new techniques to improve persistent KVs. I designed and built four novel open-source systems: TRIAD, FloDB, SILK, and KVell. For an overview, have a look at my job talk.
KVell+ [OSDI '20] addresses space amplification for queries executed under Snapshot Isolation in KVs. Frequent updates during long-running analytics queries create significant space amplification, and resulting garbage collection gives rise to latency spikes for shorter transactions. We introduce a new model for processing analytics queries based on the observation that such queries consist in large part of commutative processing of data items resulting from range-scans, in which each item in the range is read exactly once. OLCP incurs little or no space amplification or garbage collection overhead. [pdf] [code][slides][talk-OSDI by Baptiste Lepers]
KVell [SOSP '19] provides surprising insights into new storage technologies and their impact on current persistent KV designs. The emergence of fast drives shifts the bottleneck from I/O bandwidth to the CPU, making it necessary to revisit previous fundamental design assumptions, such as maintaining the sorted order of data and making use of complex synchronization primitives. [pdf] [code][slides][talk-SOSP by Baptiste Lepers]
SILK+ [TOCS '20] builds upon the SILK I/O scheduler, adding support for workloads with heterogeneous item sizes and analytics queries (i.e., range scans). SILK+ is an important addition for production workloads such as the ones at Nutanix, Pinterest, and Wikipedia, where the item sizes can differ by up to three orders of magnitude. Academic Impact: This work was an invited paper for the Special Issue of TOCS '20. [pdf]
SILK [ATC '19] addresses the issue of tail latency in log-structured merge KVs, stemming from significant interference between client work and KV maintenance operations. The interference creates a bottleneck at the I/O bandwidth level. SILK prevents tail latency spikes through a novel opportunistic I/O bandwidth scheduling mechanism. Academic Impact: This work received one of three Best Paper Awards in USENIX ATC '19 (top 3 out of 356 submissions). [pdf] [code][slides][talk-MSR]
TRIAD [ATC '17] focuses on the disk utilization of KVs. Through its three complementary techniques acting at the memory, disk and commit log levels, TRIAD drastically reduces write amplification in persistent storage and the effect of KV maintenance operations. The reduced write amplification leads to a commensurate throughput improvement for the client-facing workload. Industry Impact: This work is currently used in production at Nutanix and was featured on Mark Callaghan's Small Datum blog. [pdf] [code][slides]
FloDB [ATC '17] addresses the issue of scalability with the memory size and with the number of threads in persistent KVs, again resulting in important gains in throughput for client workloads. The main contribution is a new two-layer data-structure design which is highly concurrent and improves the data flow from clients, to memory, to disk. [pdf] [code][slides]
COMP-596 – Principles of Computer Systems. In the fall semester of 2021, I will be teaching a new course on the principles of computer systems design. The class is open to graduate and undergraduate students.
COMP-310/ECSE-427 – Operating Systems. In the winter semester of 2021 I will be co-teaching a course on the fundamentals of operating systems design and implementation together with Prof. Joseph Vybihal.
[OSDI '20] Snapshot Isolation Without Snapshots. USENIX Symposium on Operating Systems Design and Implementation 2020 (17% acceptance ratio). B. Lepers, O. Balmau, K. Gupta , W. Zwaenepoel. [pdf] [code] [slides]
[THESIS] Redesigning Persistent Key-Value Stores for Future Workloads, Hardware, and Performance Requirements. Oana Balmau. Doctoral Dissertation, The University of Sydney, 2020. Advised by Prof. Willy Zwaenepoel. PhD Committee: Dr. Ricardo Bianchini, Prof. Vijay Chidambaram, Prof. Frans Kaashoek. Winner of CORE John Makepeace Bennett Award 2021 for the best Computer Science doctoral dissertation in Australia and New Zealand [pdf].
[TOCS '20] SILK+: Preventing Latency Spikes in Log-Structured Merge Key-Value Stores Running Heterogeneous Workloads. ACM Transactions on Computer Systems Special Issue. O. Balmau, F. Dinu, W. Zwaenepoel, K. Gupta , R. Chandhiramoorthi, D. Didona. Invited paper. [pdf]
[SOSP '19] KVell: the Design and Implementation of a Fast Persistent Key-Value Store. Symposium on Operating Systems Principles 2019 (14% acceptance ratio). B. Lepers, O. Balmau, K. Gupta , W. Zwaenepoel. [pdf] [code][slides][talk]
[USENIX ATC '19] SILK: Preventing Latency Spikes in Log-Structured Merge Key-Value Stores. USENIX Annual Technical Conference 2019 (19% acceptance ratio). O. Balmau, F. Dinu, W. Zwaenepoel, K. Gupta , R. Chandhiramoorthi, D. Didona. Best Paper Award! Invited to publish in ACM Transactions on Computer Systems (TOCS) special issue. [pdf] [code][slides][talk-MSR]
[NETYS '19] The Fake News Vaccine. The International Conference on Networked Systems 2019. O. Balmau, R. Guerraoui, A-M. Kermarrec, A. Maurer, M. Pavlovic, W. Zwaenepoel. [pdf-arXiv]
[USENIX ATC '17] TRIAD: Creating Synergies Between Memory, Disk and Log in LSM Key-Value Stores. USENIX Annual Technical Conference 2017 (21% acceptance ratio). O. Balmau, D. Didona, R. Guerraoui, W. Zwaenepoel, H. Yuan, A. Arora, K. Gupta, P. Konka. [pdf] [code][slides]
[EuroSys '17] FloDB: Unlocking Memory in Persistent Key-Value Stores. The European Conference on Computer Systems 2017 (20% acceptance ratio). O. Balmau, R. Guerraoui, V. Trigonakis, I. Zablotchi. [pdf] [code][slides]
[SPAA '16] Fast and robust memory reclamation for concurrent data structures. ACM Symposium on Parallelism in Algorithms and Architectures (24% acceptance ratio). O. Balmau, R. Guerraoui, M. Herlihy, I. Zablotchi. [pdf][code]
[SmartGridComm '14] Evaluation of RPL for medium voltage power line communication. IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids. O. Balmau, D. Dzung, A. Karaağaç, V. Nesovic, A. Paunovic, Y-A. Pignolet, N. Tehrani.
[SmartGridComm '14] Recipes for faster failure recovery in Smart Grid communication networks. IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids. O. Balmau, D. Dzung, Y-A. Pignolet.
Awards and Honors
CORE John Makepeace Bennett Award 2021 for the best Computer Science doctoral dissertation in Australia and New Zealand.
USENIX ATC 2019 Best Paper Award.
University of Sydney Faculty of Engineering and IT Dean’s Postgraduate Research Scholarship.
EPFL Fellowship for Doctoral Studies.
EPFL Teaching Assistant Award for Teaching Excellence.
Brown University Presidential Fellowship for Incoming Graduate Students.
EPFL Excellence Fellowship for the Master Studies.
SIGMOD '21 '22 research track Program Committee member.
SOSP '21 Program Committee member.
OSDI '21 External Review Committee.
EuroSys '21 Program Committee member. EuroSys Doctoral Workshop '21 Program Committee member.
Outside of research, I enjoy:
Yoga. I am a certified Hatha and Yin Yoga teacher (400h), maintaining a daily asana, pranayama and meditation practice.
Dancing. I practice a variety of styles including salsa, modern, and bellydancing.
Scuba Diving and Hiking. I love exploring the underwater world and the mountains during my travels.