A service-level objective (SLO), as per the O'Reilly Site Reliability Engineering book, is a "target value or range of values for a service level that is measured by an SLI."[1] An SLO is a key element of a service-level agreement (SLA) between a service provider and a customer. SLOs are agreed upon as a means of measuring the performance of the service provider and are outlined as a way of avoiding disputes between the two parties based on misunderstanding.
There is often confusion in the use of SLAs and SLOs. The SLA is the entire agreement that specifies what service is to be provided, how it is supported, times, locations, costs, performance, and responsibilities of the parties involved. SLOs are specific measurable characteristics of the SLA such as availability, throughput, frequency, response time, or quality. These SLOs together are meant to define the expected service between the provider and the customer and vary depending on the service's urgency, resources, and budget. SLOs provide a quantitative means to define the level of service a customer can expect from a provider.[2]
The SLO are formed by setting goals for metrics (commonly called service level indicators, SLIs). As an example, an availability SLO may be defined as the expected measured value of an availability SLI over a prescribed duration (e.g. four weeks). The availability SLI used will vary based on the nature and architecture of the service. For example, a simple web service might use the ratio of successful responses served vs the total number of valid requests received. (total_success / total_valid) [3]
While Andrieux et al. define the SLO as "the quality of service aspect of the agreement. Syntactically, it is an assertion over the terms of the agreement as well as such qualities as date and time".[5] Keller and Ludwig more concisely define an SLO as "commitment to maintain a particular state of the service in a given period" with respect to the state of the SLA parameters.[6] Keller and Ludwig go on to state that while service providers will most often be the lead entity in taking on SLOs there is no firm definition as such and any entity can be responsible for an SLO. Along with this an SLO can be broken down into a number of different components.
Obliged - The entity that is required to deliver the SLO.
Validity Period - The time in which the SLO will be delivered.
Expression - This is the actual language that defines what the SLO will be.
Optionally an EvaluationEvent maybe assigned to the SLO, an EvaluationEvent is defined as the measure by which the SLO will be checked to see if it's meeting the Expression.
SLOs should generally be specified in terms of an achievement value or service level, a target measurement, a measurement period, and where and how they are measured.[2] As an example, "90% of calls to the helpdesk should be answered in less than 20 seconds measured over a one-month period as reported by the ACD system". Results can be reported as a percent of time that the target answer time was achieved and then compared to the desired service level (90%).
Type of Measure
Example SLO Requirement
Measurement Period
Availability
The application will be available 99.95% of the time
Over a year
Service Desk Response
75% of help desk calls will be answered in less than a minute
85% of help desk calls will be answered within two minutes
100% of help desk calls will be answered within three minutes
Over a month
Incident Response Time
99% of severity 1 tickets will be resolved within three hours
98% of severity 2 tickets will be resolved within eight hours
98% of severity 3 tickets will be resolved within three business days
98% of severity 4 tickets will be resolved within five business days
Over a quarter
Response Time
85% of TCP replies within 1.5 seconds of receiving a request
99.5% of TCP replies within 4 seconds of receiving a request
Over a month
Term usageedit
The SLO term is found in various scientific papers, for instance in the reference architecture of the SLA@SOI project,[7] and it is used in the Open Grid Forum document on WS-Agreement.[5]
Referencesedit
^Beyer, Jones, Petoff, Murphy. "Site Reliability Engineering: How Google Runs Production Systems". Google Site Reliability Engineering. O'Reilly. Retrieved 9 June 2023.{{cite web}}: CS1 maint: multiple names: authors list (link)
^ abRastegari, Yousef; Shams, Fereidoon (2015-12-29). "Optimal Decomposition of Service Level Objectives into Policy Assertions". The Scientific World Journal. 2015: 465074. doi:10.1155/2015/465074. ISSN 2356-6140. PMC4709918. PMID 26962544.
^Hidalgo, Alex (August 2020). Implementing Service Level Objectives (1 ed.). O'Reilly Media, Inc. ISBN9781492076766.
^Rick Sturm, Wayne Morris "Foundations of Service Level Management", April 2000, Pearson.
^ abAlain Andrieux, Karl Czajkowski, Asit Dan, Kate Keahey, Heiko Ludwig, Toshiyuki Nakata, Jim Pruyne, John Rofrano, Steve Tuecke, Ming Xu "Web Services Agreement Specification (WS-Agreement)", GFD-R-P.107, March 2007, Open Grid Forum.
^Alexander Keller, Heiko Ludwig "The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services", Journal of Network and Systems Management, Vol 11, n. 1, March 2003.
^Jens Happe, Wolfgang Theilmann, Andrew Edmonds, and Keven T. Kearney "A Reference Architecture for Multi-Level SLA Management" in "Service Level Agreements for Cloud Computing", eds. Wieder, Philipp and Butler, Joe M. and Theilmann, Wolfgang and Yahyapour, Ramin, Springer New York, 2011, DOI:10.1007/978-1-4614-1614-2_2
External linksedit
Service Level Objectives
What are SLOs? How service-level objectives work with SLIs to deliver on SLAs
SLA vs. SLO vs. SLI: What’s the difference?
April 13, 2024
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This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Service level objective news newspapers books scholar JSTOR December 2013 Learn how and when to remove this template message A service level objective SLO as per the O Reilly Site Reliability Engineering book is a target value or range of values for a service level that is measured by an SLI 1 An SLO is a key element of a service level agreement SLA between a service provider and a customer SLOs are agreed upon as a means of measuring the performance of the service provider and are outlined as a way of avoiding disputes between the two parties based on misunderstanding Contents 1 Overview 2 Examples 3 Term usage 4 References 5 External linksOverview editThere is often confusion in the use of SLAs and SLOs The SLA is the entire agreement that specifies what service is to be provided how it is supported times locations costs performance and responsibilities of the parties involved SLOs are specific measurable characteristics of the SLA such as availability throughput frequency response time or quality These SLOs together are meant to define the expected service between the provider and the customer and vary depending on the service s urgency resources and budget SLOs provide a quantitative means to define the level of service a customer can expect from a provider 2 The SLO are formed by setting goals for metrics commonly called service level indicators SLIs As an example an availability SLO may be defined as the expected measured value of an availability SLI over a prescribed duration e g four weeks The availability SLI used will vary based on the nature and architecture of the service For example a simple web service might use the ratio of successful responses served vs the total number of valid requests received total success total valid 3 Examples editSturm and Morris argue 4 that SLOs must be Attainable Repeatable Measurable Understandable Meaningful Controllable Affordable Mutually acceptableWhile Andrieux et al define the SLO as the quality of service aspect of the agreement Syntactically it is an assertion over the terms of the agreement as well as such qualities as date and time 5 Keller and Ludwig more concisely define an SLO as commitment to maintain a particular state of the service in a given period with respect to the state of the SLA parameters 6 Keller and Ludwig go on to state that while service providers will most often be the lead entity in taking on SLOs there is no firm definition as such and any entity can be responsible for an SLO Along with this an SLO can be broken down into a number of different components Obliged The entity that is required to deliver the SLO Validity Period The time in which the SLO will be delivered Expression This is the actual language that defines what the SLO will be Optionally an EvaluationEvent maybe assigned to the SLO an EvaluationEvent is defined as the measure by which the SLO will be checked to see if it s meeting the Expression SLOs should generally be specified in terms of an achievement value or service level a target measurement a measurement period and where and how they are measured 2 As an example 90 of calls to the helpdesk should be answered in less than 20 seconds measured over a one month period as reported by the ACD system Results can be reported as a percent of time that the target answer time was achieved and then compared to the desired service level 90 Type of Measure Example SLO Requirement Measurement PeriodAvailability The application will be available 99 95 of the time Over a yearService Desk Response 75 of help desk calls will be answered in less than a minute 85 of help desk calls will be answered within two minutes100 of help desk calls will be answered within three minutes Over a monthIncident Response Time 99 of severity 1 tickets will be resolved within three hours 98 of severity 2 tickets will be resolved within eight hours98 of severity 3 tickets will be resolved within three business days98 of severity 4 tickets will be resolved within five business days Over a quarterResponse Time 85 of TCP replies within 1 5 seconds of receiving a request 99 5 of TCP replies within 4 seconds of receiving a request Over a monthTerm usage editThe SLO term is found in various scientific papers for instance in the reference architecture of the SLA SOI project 7 and it is used in the Open Grid Forum document on WS Agreement 5 References edit Beyer Jones Petoff Murphy Site Reliability Engineering How Google Runs Production Systems Google Site Reliability Engineering O Reilly Retrieved 9 June 2023 a href Template Cite web html title Template Cite web cite web a CS1 maint multiple names authors list link a b Rastegari Yousef Shams Fereidoon 2015 12 29 Optimal Decomposition of Service Level Objectives into Policy Assertions The Scientific World Journal 2015 465074 doi 10 1155 2015 465074 ISSN 2356 6140 PMC 4709918 PMID 26962544 Hidalgo Alex August 2020 Implementing Service Level Objectives 1 ed O Reilly Media Inc ISBN 9781492076766 Rick Sturm Wayne Morris Foundations of Service Level Management April 2000 Pearson a b Alain Andrieux Karl Czajkowski Asit Dan Kate Keahey Heiko Ludwig Toshiyuki Nakata Jim Pruyne John Rofrano Steve Tuecke Ming Xu Web Services Agreement Specification WS Agreement GFD R P 107 March 2007 Open Grid Forum Alexander Keller Heiko Ludwig The WSLA Framework Specifying and Monitoring Service Level Agreements for Web Services Journal of Network and Systems Management Vol 11 n 1 March 2003 Jens Happe Wolfgang Theilmann Andrew Edmonds and Keven T Kearney A Reference Architecture for Multi Level SLA Management in Service Level Agreements for Cloud Computing eds Wieder Philipp and Butler Joe M and Theilmann Wolfgang and Yahyapour Ramin Springer New York 2011 DOI 10 1007 978 1 4614 1614 2 2External links editService Level Objectives What are SLOs How service level objectives work with SLIs to deliver on SLAs SLA vs SLO vs SLI What s the difference Retrieved from https en wikipedia org w index php title Service level objective amp oldid 1187466012, wikipedia, wiki, book, books, library,
