Site Reliability Engineering (SRE) and DevOps share a goal of building a bridge between development and operations. We'll explore and compare both approaches.
Wondering to yourself, which is better for your company, SRE or DevOps? Neither SRE or DevOps is “better,” exactly, since they’re similar yet different in a few key ways:
SRE and DevOps share the same foundational principles.
SRE can be viewed as a specific implementation of DevOps.
They share the same goal of rapidly delivering reliable software.
Devops teams focus on “what” needs to be done, SRE teams focus on “how.”
What is SRE?
SRE, or site reliability engineering, is a methodology developed by Google engineer Ben Treynor Sloss in 2003. The goal of SRE is to align engineering goals with customer satisfaction. Teams achieve this by focusing on reliability. SRE is an implementation of DevOps, a similar school of thought. Google is also responsible for bringing these two methods together. In this article, we'll break down more of what this looks like in practice.
SLIs and SLOs
Reliability is a subjective quality based on your customers’ experiences. SRE allows you to measure how happy your customers are by using SLIs. SLIs, or service level indicators, are metrics that show how your service is performing at key points on a user journey. SLOs then set a limit for how much unreliability the customer will tolerate for that SLI.
SRE teaches us that 100% uptime is impossible. Some amount of failure is inevitable. Because of that, incident response is a core SRE best practice. Responding to incidents faster reduces customer impact. But, you need the processes in place to enable this. There are many components to incident response, including:
Incident classification: Sort incidents into categories based severity and area affected. This allows you to triage incidents and alert the right people.
Alerting and on-call systems: Determine people available to respond to incidents as needed. Set guidelines for who gets called and when. Make sure to balance schedules and be compassionate.
Runbooks: These are documents that guide responders through a particular task. Runbooks are particularly useful for incident response. They include things to check for, and steps to take for each possibility. They’re made as straightforward as possible to reduce toil. Automating runbooks can reduce toil further.
Incident retrospectives: SRE advocates learning as much as possible from each incident. Retrospectives document timelines, key communications, resources used, relevant monitoring data, and more. Review these documents as a group. Use them to determine follow-up tasks or revise runbooks and other resources.
Nobody expects perfection. Some amount of unreliability is acceptable to your customers. As long as your performance meets your SLO, customers will stay happy with your services. The wiggle room you have before your SLO is breached is the error budget.
Your error budget can help you make decisions about prioritization. For instance, services with lots of remaining error budget can accelerate development. When the error budget depletes, teams know it's time to focus on reliability.. Through this decision-making tool, SRE allows operations to influence development in a way that reflects customer needs.
The cultural changes of SRE are as important (if not more) than the process changes. The cultural lessons of SRE include:
Blamelessness: When something goes wrong, it is never the fault of an individual. Assume that everyone acts in good faith and does their best with the information available to them. Work together to find systemic causes for the incident.
Psychological safety: Teammates feel secure. They should be comfortable raising issues and expressing concerns without retributions. This encourages creativity, curiosity, and innovation.
Celebrating failure: Incidents aren’t setbacks, but unplanned investments in reliability. By experiencing an incident and learning from it, the system becomes more resilient.
What is DevOps?
DevOps is a set of practices that connects the development of software with its maintenance and operations. Its name reflects these two parts: Development and Operations. DevOps originated from a collection of previous practices. These include the Agile development system, the Toyota Way, and Lean manufacturing. The term DevOps became well-known in the early 2010s.
The primary goal of DevOps is to reduce the time between making a change in code and that change reaching the customers, without impacting reliability. It seeks to align the goals of development with organizational needs to create business value. In this way, the goals of SRE and DevOps are very similar. Both focus on customer impact and efficiency. But, the methods they use to achieve this vary.
DevOps seeks to increase the frequency of new deployments of code. Faster, more incremental changes allow a more attuned response to customer needs. It also reduces the chance of major incidents caused by large, infrequent deployments.
Collaboration between development and operations
A core tenet of DevOps is to remove silos between development and operations teams. Rather than development “throwing code over the wall” for operations to handle, the teams work together throughout the service’s lifecycle.
Here are some DevOps practices that encourage cooperation between development and operations:
Alignment on goals: Ensure both teams understand what they’re working towards. Shared roadmaps and agreed-upon metrics help with alignment. Use customer impact as a common priority.
Develop with operations in mind: Development and operations should collaborate on how development should proceed. Operations makes suggestions that help them maintain the code in production.
Availability of data and resources
Monitoring data for DevOps is a big deal. DevOps advocates measuring valuable data and using it as your basis for decision making. By default, data should be accessible across the organization.
Simply having a lot of data available isn’t enough to make good decisions. Metrics should be contextualized to provide deeper insights. Make sure that you're setting up monitoring that helps you learn about your system. Having too much data can actually make decision making more difficult.
Automate where possible
Like SRE, DevOps advocates for automating wherever possible. Where SRE focuses on automating to increase consistency and reduce toil, DevOps automates to tighten the development cycle. By removing manual steps in testing and deployment, teams can achieve a faster release frequency.
How SRE connects to DevOps
You can implement both DevOps and SRE into your organization. A helpful way to combine the methodologies is to consider SRE as a way to achieve the goals of DevOps. This doesn’t mean SRE is better than DevOps. Focusing on the goals of DevOps instead of the process-focused approach of SRE is also helpful. Drawing from both methodologies as appropriate provides the best way forward.
SRE as an implementation of DevOps
SRE is a method of implementing the goals of DevOps. Here are some of the common goals of DevOps, and how SRE practices can help achieve them:
Remove silos: SRE achieves this by creating documentation that the entire organization can use and learn from. Lessons from incidents are fed back into development practices through incident retrospectives.
Change gradually: SRE advocates incremental rollouts and A/B testing. This effectively makes the change more gradual, achieving the same goal of reducing the impact of failure.
Use tools and automate: many SRE tools reduce manual toil. Whenever you automate or simplify a process, you reduce toil and increase consistency. You also accelerate the process, achieving DevOps goals.
Metric-based decisions: SRE practices encourage monitoring everything and then constructing deep metrics. These will give you the insights you need to make smart decisions.
Accept failure: Not only does SRE accept failure, it celebrates it and utilizes it. By strategically using error budgets, you can accelerate development while maintaining reliability.
DevOps determines what needs to be done, whereas SRE determines how it will be done. DevOps captures a vision of a system that is developed efficiently and reliably. SRE builds processes and values that result in this system. You can establish your goals using DevOps principles, and then implement SRE to achieve them.
SRE vs. DevOps philosophy
SRE and DevOps share many philosophies and principles. Some that they share include:
Placing value on collaboration across teams, particularly between development and operations
Automation and toil reduction are key to increasing consistency and helping humans
Improvement is always possible. There is always value in reviewing and revising policy
Customer satisfaction is the most important concern. It’s the motivator for developing quickly and reliably
Sharing knowledge, whether through monitoring data, incident retrospectives, or codified best practices, is key to making good decisions
Failure is inevitable, and something to embrace and learn from
However, SRE and DevOps also have some differences in philosophy. Often these come down to priority. Some differences include:
DevOps advocates for a fluid approach to problem solving. SRE creates codified and consistent processes.
SRE implements practices such as chaos engineering to further increase reliability. DevOps is more focused on the development lifecycle, so these extra practices don’t typically emerge.
SRE generally advocates for lower risk tolerance than DevOps. Working under metrics like SLOs, SRE will implement policies such as code freezes to avoid a breach. DevOps is more comfortable adjusting standards of reliability as development requires.
DevOps usually operates with improving development speed as a primary goal. SRE considers increased development velocity a byproduct of error budgeting and better incident response.
Both SRE and DevOps have a major focus on automation, but SRE’s approach is more widespread. DevOps primarily automates to increase development speed and focuses on steps in the development cycle. SRE automates any processes it can, from chaos tests to incident management.
SRE vs DevOps teams
When implementing either SRE or DevOps in your organization, you’ll need to consider how these changes will actually take place. Will you:
Build policies and procedures collaboratively and rely on everyone to follow them?
Assign implementation duties to particular engineers in addition to their normal tasks?
Reallocate engineers to be on a team wholly devoted to rolling out new procedures?
Hire new engineers to build out your implementation team?
Depending on the maturity of your organization and your needs, different approaches will be more efficient. You should consider how you want to structure your DevOps and SRE hires.
Structures for SRE and DevOps teams
Both DevOps and SRE teams vary based on how centralized they are. At one end is a centralized team, which creates tools, infrastructure, and processes that the entire organization shares.
The other extreme is a distributed team. DevOps/SRE engineers are assigned to individual teams and projects. They handle maintaining the reliability and velocity goals for each team.
The SRE vs DevOps role
Every engineer can work to implement DevOps and SRE best practices without holding the title of DevOps Engineer or SRE. However, if you do have dedicated staff with this title, here are the main distinctions between the responsibilities:
Starting your SRE journey with Blameless
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About Emily Arnott
Emily is the Community Relations Manager at Blameless, where she fosters a place for discussing the latest in SRE. She has also presented talks at SREcon, Conf42, and Chaos Carnival. Follow Emily on Twitter.