Urs Hölzle

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Urs Hölzle
Urs Holzle 2014.jpg
Urs Hölzle (2014)
Alma materETH Zurich
Stanford University
Known forJIT compilers, cloud infrastructure
AwardsAAAS Fellow, ACM Fellow, Fulbright Scholar, NAE Member
Scientific career
InstitutionsUniversity of California, Santa Barbara
ThesisAdaptive optimization for Self: Reconciling High Performance with Exploratory Programming (1994)
Doctoral advisorDavid Ungar
John L. Hennessy

Urs Hölzle (German pronunciation: [ˈʊrs ˈhœltslɛ]) is a Swiss software engineer and technology executive. He is the senior vice president of technical infrastructure and Google Fellow at Google. As Google's eighth employee and its first VP of Engineering, he has shaped much of Google's development processes and infrastructure.[1]

Hölzle was elected a member of the National Academy of Engineering in 2013 for contributions to the design, operation, and energy efficiency of large-scale data centers.


Before joining Google, Hölzle was an Associate Professor of Computer Science at University of California, Santa Barbara. He received a master's degree in computer science from ETH Zurich in 1988 and was awarded a Fulbright scholarship that same year. In 1994, he earned a Ph.D. from Stanford University, where his research focused on programming languages and their efficient implementation. Via a startup founded by Hölzle, David Griswold, and Lars Bak (see Strongtalk), that work then evolved into a high-performance Java VM named HotSpot, acquired by Sun's JavaSoft unit in 1997 and from there became Sun's premier JVM implementation.

In 1999 he joined Google and became its first Vice President of Engineering later that year and influenced Google's corporate and engineering culture.[1] While he led various areas during the early years of the company, including operations, search, and Gmail, he is best known for his work leading the infrastructure systems underpinning Google's applications, and for their focus on both efficiency and scalability. With Jeff Dean and Luiz Barroso he designed the initial distributed architecture for Google.[2] This work was recognized by the Association for Computing Machinery who named him a Fellow for the design, engineering and operation of energy efficient large-scale cloud computing systems.[3] He is also credited for creating Google Gulp for April Fool's Day in 2005.

Data centers and servers[edit]

He led the design of Google's efficient data centers which are said to use less than half the power of a conventional data center.[4] In 2014 he received The Economist's Innovation Award for his datacenter efficiency work.[5] With Luiz Barroso, he wrote The Datacenter as a Computer: An Introduction to the Design of Warehouse-Scale Machines.[6] Now in its third edition, the book is the most downloaded textbook at Morgan Claypool[7] and is widely used in undergraduate and graduate Computer Science education. For his contributions to the design, operation, and energy efficiency of large-scale data centers, Hölzle was elected into the National Academy of Engineering in 2013.[8]

In June 2007, he introduced the Climate Savers Computing Initiative together with Pat Gelsinger which aimed to halve the power consumption of desktop computers and servers. In 2012, after mobile computing and enhanced awareness of datacenter energy costs had contributed to significant improvements in energy efficiency, CSCI merged with the Green Grid consortium.[9]

Also in 2007, he and Luiz Barroso wrote "The Case for Energy Proportional Computing" which argued that servers should be designed to use power in proportion to their current load, because they spend much of their time being only partially loaded. This paper is often credited for spurring CPU manufacturers to make their designs much more energy efficient.[10] Today, energy proportional computing has become a standard goal for both server and mobile uses.


Starting in 2005, Hölzle's team began to develop datacenter networking hardware because off-the-shelf network equipment could not scale to the demands of large data centers. Using Clos network topologies based on commodity switch chips, these datacenter networks scaled from an initial 10 Tbit/s to 1,000 Tbit/s a decade later.[11] Initially esoteric and kept a secret, today this approach is standard for large datacenter networks; virtually all hyperscale datacenter operators use similar approaches.[12][13]

In 2012, Hölzle introduced "the G-Scale Network" on which Google had begun managing its petabyte-scale internal data flow via OpenFlow, an open source software system jointly devised by scientists at Stanford and the UC Berkeley and promoted by the Open Networking Foundation. In 2021, this work was recognized by the ACM SIGCOMM Networking Systems Award.[14] The internal data flow, or network, is distinct from the one that connects users to Google services (Search, Gmail, YouTube, etc.). In the process of describing the new network, Hölzle also confirmed more about Google's making of its own networking equipment like routers and switches for G-Scale; and said the company wanted, by being open about the changes, to "encourage the industry — hardware, software and ISP's — to look down this path and say, 'I can benefit from this.'" He said network utilization was nearing 100% of capacity, a dramatic efficiency improvement.[15]

Google's teams also heavily contributed to software-defined networking, creating or contributing to key building blocks used in many networks today, including OpenConfig for vendor-neutral, model-driven network management; gRPC for fast RPCs, protobuf for data interchange, OpenTelemetry for tracing, and the Istio service mesh.

Environmental work[edit]

In 2007, Hölzle announced that Google would be carbon neutral starting that year, using individually selected and monitored carbon offset projects.[16] In the same year, Google started the RE<C initiative ("Renewable Energy less than (cheaper than) coal")[17] to develop cheaper forms of renewable energy, but four years later Hölzle announced the end of that strategy, dropping development of "solar thermal" electricity (for example with BrightSource Energy) because it was not keeping pace with the rapid price decline of another solar technology – photovoltaics.[18] Starting in 2010,[19] Google began buying renewable energy from new wind and solar farms to cover the energy needs for all its datacenters.[20] Since 2017 it has been buying enough renewable energy to offset 100% of its usage[21] and now is the world's largest corporate buyer of renewable energy.[22] In 2017, Hölzle received the CK Prahalad Award "for bringing about innovations and radical efficiencies in data center technology and increasing corporate purchasing of renewable energy" and for "not only accelerating Google’s sustainability, [but] also cutting a path for other companies to follow suit.”[23]

He is a board member of the US World Wildlife Fund.[24]

Academic honors[edit]

Hölzle is a Fulbright scholar, a member of the National Academy of Engineering,[8] and a Fellow of the Association for Computing Machinery (2009),[25] the AAAS (2017),[26] and the Swiss Academies of Arts and Sciences.[27]

Google culture[edit]

As Google's eighth employee and its first VP of Engineering, Hölzle shaped much of Google's development processes and infrastructure. In a book about the early days of Google, Doug Edwards credits him with defining much of Google's engineering and corporate culture.[1] For example, he is said to have instituted Google's practice of code reviews for every change, the culture of using blameless postmortems to learn from mistakes rather than find out whose fault it was,[28] and a focus on using technical interviews to identify the best candidates. He recruited many of Google's early engineers, including Jeff Dean.

He was known for his self-deprecating humor; for example, his initial job title was Search Engine Mechanic "because everything was broken".[29]

Hölzle also influenced Google's office culture by bringing his dog Yoshka to work. In 2004 Yoshka even "authored" a blog post, and today Google declares itself a "dog company".[30] The cafe in Building 43 of the Googleplex is named Yoshka's Cafe[31] in honor of Google's first dog.

In July 2021 he was criticised[32] for a perceived 'hypocritical' approach to remote working; opposing it strongly for others, while relocating to New Zealand. However, shortly after Hölzle's transfer was announced, Google approved the large majority of employee applications, permitting 8,500 other employees to work remotely as well.[33]


  1. ^ a b c "I'm Feeling Lucky", Doug Edwards, Houghton Mifflin 2012
  2. ^ Barroso, L.A.; Dean, J.; Holzle, U. (March 2003). "Web search for a planet: The Google cluster architecture". IEEE Micro. 23 (2): 22–28. doi:10.1109/MM.2003.1196112. ISSN 1937-4143.
  3. ^ "Urs Hoelzle". awards.acm.org. Retrieved 2021-05-01.
  4. ^ Google's Green Datacenter
  5. ^ Economist, December 6, 2014
  6. ^ Luiz André Barroso and Urs Hölzle, The Datacenter as a Computer: An Introduction to the Design of Warehouse-Scale Machines, Morgan & Claypool, 2009. ISBN 9781598295573
  7. ^ "Most popular downloads" https://www.morganclaypool.com/action/showMostReadArticles?journalCode=cac&
  8. ^ a b > NAE press release
  9. ^ "The Green Grid and Climate Savers Will Merge" https://www.datacenterknowledge.com/archives/2012/07/20/the-green-grid-climate-savers-computing-initiative-merge
  10. ^ "Server Efficiency: Aligning Energy Use With Workloads", Datacenter Knowledge, June 12, 2012
  11. ^ "Jupiter Rising: A Decade of Clos Topologies and Centralized Control in Google’s Datacenter Network" https://research.google/pubs/pub43837/
  12. ^ "Introducing data center fabric, the next-generation Facebook data center network". Facebook Engineering. 2014-11-14. Retrieved 2021-05-01.
  13. ^ Jain, Sushant; Kumar, Alok; Mandal, Subhasree; Ong, Joon; Poutievski, Leon; Singh, Arjun; Venkata, Subbaiah; Wanderer, Jim; Zhou, Junlan; Zhu, Min; Zolla, Jon (2013-08-27). "B4: experience with a globally-deployed software defined wan". ACM SIGCOMM Computer Communication Review. 43 (4): 3–14. doi:10.1145/2534169.2486019. ISSN 0146-4833.
  14. ^ "SIGCOMM Networking Systems Award | acm sigcomm". www.sigcomm.org. Retrieved 2022-04-01.
  15. ^ Levy, Steven, "Going With the Flow: Google's Secret Switch to the Next Wave of Networking", Wired, April 17, 2012. Retrieved 2012-04-17.
  16. ^ "Carbon neutrality by end of 2007" https://googleblog.blogspot.com/2007/06/carbon-neutrality-by-end-of-2007.html
  17. ^ "RE<C Initiative" https://www.google.org/rec.html?theme=greenz_dev
  18. ^ "Google cans concentrated solar power project", REVE, November 24, 2011. Retrieved 2012-05-29.
  19. ^ "Google inks 20-year deal to buy wind power for data centers" https://www.infoworld.com/article/2625618/google-inks-20-year-deal-to-buy-wind-power-for-data-centers.amp.html
  20. ^ Google's Green PPAs https://static.googleusercontent.com/media/www.google.com/en//green/pdfs/renewable-energy.pdf
  21. ^ "100% renewable is just the beginning" https://sustainability.google/projects/announcement-100/
  22. ^ "Tech giants power record surge in renewable energy sales" https://www.theguardian.com/environment/2020/jan/28/google-tech-giants-spark-record-rise-in-sales-of-renewable-energy
  23. ^ "C.K. Prahalad Award". CEF. Retrieved 2022-05-17.
  24. ^ Urs Hölzle. WWF webpage.
  25. ^ ACM Fellows>Urs Hoelzle, Association for Computing Machinery webpage.
  26. ^ AAAS 2017 Fellows, AAAS webpage.
  27. ^ Full members>Hölzle, Dr Urs, SATW webpage.
  28. ^ "Site Reliability Engineering, Chapter 15 - Postmortem Culture: Learning from Failure". sre.google. Retrieved 2021-05-30.{{cite web}}: CS1 maint: url-status (link)
  29. ^ magazin, Andrea Rungg, manager. "Urs Hölzle: Googles Mitarbeiter Nummer 8". www.manager-magazin.de (in German). Retrieved 2021-05-30.
  30. ^ "Working from home is ruff. Dooglers make it a little better". Google. 2020-10-16. Retrieved 2021-05-30.
  31. ^ "Yoshka's · Mountain View, CA 94043". Yoshka's · Mountain View, CA 94043. Retrieved 2021-05-30.
  32. ^ "Google's 'hypocritical' remote work policies anger employees". Retrieved 2021-07-09.
  33. ^ "Bloomberg - Google Approves Most Staff Requests to Relocate or Work Remotely". www.bloomberg.com. Retrieved 2021-12-26.{{cite web}}: CS1 maint: url-status (link)

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