Performance Of IT Infrastructure Author Liam Smith
- 1. IT Infrastructure Architecture (chapter 2) Infrastructure Building Blocks and Concepts Shaharyar Islam
- 2. Introduction Performance is a typical hygiene factor Nobody notices a highly performing system But when a system is not performing well enough, users quickly start complaining Shaharyar Islam
- 3. Perceived performance Perceived performance refers to how quickly a system appears to perform its task In general, people tend to overestimate their own patience People tend to value predictability in performance When the performance of a system is fluctuating, users remember a bad experience Even if the fluctuation is relatively rare Shaharyar Islam
- 4. Perceived performance Inform the user about how long a task will take Progress bars Splash screens Shaharyar Islam
- 6. Performance during infrastructure design A solution must be designed, implemented, and supported to meet the performance requirements Even under increasing load Calculating performance of a system in the design phase is: Extremely difficult Very unreliable Shaharyar Islam
- 7. Performance during infrastructure design Performance must be considered: When the system works as expected When the system is in a special state, like: Failing parts Maintenance state Performing backup Running batch jobs Some ways to do this are: Benchmarking Using vendor experience Prototyping User Profiling Shaharyar Islam
- 8. Benchmarking A benchmark uses a specific test program to assess the relative performance of an infrastructure component Benchmarks compare: Performance of various subsystems Across different system architectures Shaharyar Islam
- 9. Benchmarking Benchmarks comparing the raw speed of parts of an infrastructure Like the speed difference between processors or between disk drives Not taking into account the typical usage of such components Examples: Million Instructions Per Second – MIPS Shaharyar Islam
- 10. Vendor experience The best way to determine the performance of a system in the design phase: use the experience of vendors They have a lot of experience running their products in various infrastructure configurations Vendors can provide: Tools Figures Best practices Shaharyar Islam
- 11. Prototyping Also known as proof of concept (PoC) Prototypes measure the performance of a system at an early stage Building prototypes: Hiring equipment from suppliers Using datacenter capacity at a vendor’s premise Using cloud computing resources Focus on those parts of the system that pose the highest risk, as early as possible in the design process Shaharyar Islam
- 12. User profiling Predict the load a new software system will pose on the infrastructure before the software is actually built Get a good indication of the expected usage of the system Steps: Define a number of typical user groups (personas) Create a list of tasks perform on the new system Decompose tasks to infrastructure actions Estimate the load per infrastructure action Calculate the total load Shaharyar Islam
- 13. User profiling tasks Persona Number of users per persona System task Infrastructure load as a result of the system task Frequency Data entry officer 100 Start application Read 100 MB data from SAN Once a day Data entry officer 100 Start application Transport 100 MB data to workstation Once a day Data entry officer 100 Enter new data Transport 50 KB data from workstation to server 40 per hour Data entry officer 100 Enter new data Store 50 KB data to SAN 40 per hour Data entry officer 100 Change existing data Read 50 KB data from SAN 10 per hour Shaharyar Islam
- 14. User profiling Infrastructure load Infrastructure load Per day Per second Data transport from server to workstation (KB) 10,400,000 361.1 Data transport from workstation to server (KB) 2,050,000 71.2 Data read from SAN (KB) 10,400,000 361.1 Data written to SAN (KB) 2,050,000 71.2 Shaharyar Islam
- 15. Performance of a running system Shaharyar Islam
- 16. Managing bottlenecks The performance of a system is based on: The performance of all its components The interoperability of various components A component causing the system to reach some limit is referred to as the bottleneck of the system Every system has at least one bottleneck that limits its performance If the bottleneck does not negatively influence performance of the complete system under the highest expected load, it is OK Shaharyar Islam
- 17. Performance testing Load testing - shows how a system performs under the expected load Stress testing - shows how a system reacts when it is under extreme load Endurance testing - shows how a system behaves when it is used at the expected load for a long period of time Shaharyar Islam
- 18. Performance testing - Breakpoint Ramp up the load Start with a small number of virtual users Increase the number over a period of time The test result shows how the performance varies with the load, given as number of users versus response time. Shaharyar Islam
- 19. Performance testing Performance testing software typically uses: One or more servers to act as injectors Each emulating a number of users Each running a sequence of interactions A test conductor Coordinating tasks Gathering metrics from each of the injectors Collecting performance data for reporting purposes Shaharyar Islam
- 20. Performance testing Performance testing should be done in a production-like environment Performance tests in a development environment usually lead to results that are highly unreliable Even when underpowered test systems perform well enough to get good test results, the faster production system could show performance issues that did not occur in the tests To reduce cost: Use a temporary (hired) test environment Shaharyar Islam
- 22. Increasing performance on upper layers 80% of the performance issues are due to badly behaving applications Application performance can benefit from: Database and application tuning Prioritizing tasks Working from memory as much as possible (as opposed to working with data on disk) Making good use of queues and schedulers Typically more effective than adding compute power Shaharyar Islam
- 23. Disk caching Disks are mechanical devices that are slow by nature Caching can be implemented i: Disks Disk controllers Operating system All non-used memory in operating systems is used for disk cache Over time, all memory gets filled with previously stored disk requests and prefetched disk blocks, speeding up applications. Cache memory: Stores all data recently read from disk Stores some of the disk blocks following the recently read disk blocks Shaharyar Islam
- 24. Web proxies When users browse the internet, data can be cached in a web proxy server A web proxy server is a type of cache Earlier accessed data can be fetched from cache, instead of from the internet Benefits: Users get their data faster All other users are provided more bandwidth to the internet, as the data does not have to be downloaded again Shaharyar Islam
- 25. Operational data store An Operational Data Store (ODS) is a read-only replica of a part of a database, for a specific use Frequently used information is retrieved from a small ODS database The main database is used less for retrieving information The performance of the main database is not degraded Shaharyar Islam
- 26. Front-end servers Front-end servers serve data to end users Typically web servers To increase performance, store static data on the front-end servers Pictures are a good candidate Significantly lowers the amount of traffic to back-end systems In addition, a reverse proxy can be used Automatically cache most requested data Shaharyar Islam
- 27. In-memory databases In special circumstances, entire databases can be run from memory instead of from disk In-memory databases are used in situations where performance is crucial Real-time SCADA systems High performance online transaction processing (OLTP) systems As an example, in 2011 SAP AG introduced HANA, an in-memory database for SAP systems Special arrangements must be made to ensure data is not lost when a power failure occurs Shaharyar Islam
- 28. Scalability Scalability indicates the ease in with which a system can be modified, or components can be added, to handle increasing load Two ways to scale a system: Vertical scaling (scale up) - adding resources to a single component Horizontal scaling (scale out) - adding more components to the infrastructure Shaharyar Islam
- 29. Scalability – Vertical scaling Adding more resources, for example: Server: more memory, CPU’s Network switch: adding more ports Storage: Replace small disks by larger disks Vertical scaling is easy to do It quickly reaches a limit The infrastructure component is “full” Shaharyar Islam
- 30. Scalability – Horizontal scaling Adding more components to the infrastructure, for example: Adding servers to a web server farm Adding disk cabinets to a storage system In theory, horizontal scaling scales much better Be aware of bottlenecks Doubling the number of components does not necessarily double the performance Horizontal scaling is the basis for cloud computing Applications must be aware of scaling infrastructure components Shaharyar Islam
- 32. Load balancing Load balancing uses multiple servers that perform identical tasks Examples: Web server farm Mail server farm FTP (File Transfer Protocol) server farm A load balancer spreads the load over the available machines Checks the current load on each server in the farm Sends incoming requests to the least busy server Shaharyar Islam
- 34. Load balancing Advanced load balancers can spread the load based on: The number of connections a server has The measured response time of a server The application running on a load balanced system must be able to cope with the fact that each request can be handled by a different server The load balancer should contain the states of the application The load balancing mechanism can arrange that a user’s session is always connected to the same server If a server in the server farm goes down, its session information becomes inaccessible and sessions are lost Shaharyar Islam
- 35. Load balancing A load balancer increases availability When a server in the server farm is unavailable, the load balancer notices this and ensures no requests are sent to the unavailable server until it is back online again The availability of the load balancer itself is very important Load balancers are typically setup in a failover configuration Shaharyar Islam
- 36. Load balancing Network load balancing: Spread network load over multiple network connections Most network switches support port trunking Multiple Ethernet connections are combined to get a virtual Ethernet connection providing higher throughput The load is balanced over the connections by the network switch Storage load balancing: Using multiple disks to spread the load of reads and writes Use multiple connections between servers and storage systems Shaharyar Islam
- 37. High performance clusters High performance clusters provide a vast amount of computing power by combining many computer systems A large number of cheap off the-shelf servers can create one large supercomputer Used for calculation-intensive systems Weather forecasts Geological research Nuclear research Pharmaceutical research TOP500.org Shaharyar Islam
- 38. Grid Computing A computer grid is a high performance cluster that consists of systems that are spread geographically The limited bandwidth is the bottleneck Examples: SETI@HOME CERN LHC Computing Grid (140 computing centers in 35 countries) Broker firms exist for commercial exploitation of grids Security is a concern when computers in the grid are not under control Shaharyar Islam
- 39. Design for use Performance critical applications should be designed as such Tips: Know what the system will be used for A large data warehouse needs a different infrastructure design than an online transaction processing system or a web application Interactive systems are different than batch oriented systems When possible, try to spread the load of the system over the available time Shaharyar Islam
- 40. Design for use In some cases, special products must be used for certain systems Real-time operating systems In-memory databases Specially designed file systems Use standard implementation plans that are proven in practice Follow the vendor's recommended implementation Have the vendors check the design you created Move rarely used data from the main systems to other systems Moving old data to a large historical database can speed up a smaller sized database Shaharyar Islam
- 41. Capacity management Capacity management guarantees high performance of a system in the long term To ensure performance stays within acceptable limits, performance must be monitored Trend analyses can be used to predict performance degradation Anticipate on business changes (like forthcoming marketing campaigns) Shaharyar Islam