A very basic overview of different architectural concepts, buzzwords and issues regarding architecture of (distributed) systems.

1. System architecture
DDVE 2012

2. A few principles
Components involved in an internet application
Cloud computing
Optimizing and scaling up

3. Principles of architecture
Durability - should last for long in good condition
Utility - should be useful and fulfill its function
Beauty - should make people happy
"Firmitas, Utilitas, Venustas" - Vitruvius, 1th century BC

4. Principles of software
architecture

5. 1. Reliability
Probability of error-free operation

6. 2. Efficiency
Ability to fulfill the task in the most optimum way
Not to be confused with performance

7. 3. Usability
Ease of use of the system
Learnability, Efficiency, Memorability, Errors,
Satisfaction

8. 4. Maintainability
Ability to adapt to change
Portability (to a different environment)
Transferrability (to another team)

9. Components involved in
an internet application

10. Server
A computer program servicing requests from
other programs (clients)
Server (hardware) - a computer dedicated to
running one or more such service

11. Database Server
Organized collection of data together with
management software
Oracle, MySQL, PostgreSQL, HBase, Cassandra

12. Web Server
Software serving HTTP requests
The engine behind websites, small or large
Apache, IIS (Microsoft), nginx,

13. Load balancer
Stands in front of a cluster of web servers
Distributes requests between cluster nodes to even
out the load
Provides failover when one node fails
F5 BIG-IP, Cisco, Apache

14. Web Accelerator
Frees up backend server by caching static content
Improves load speeds by compressing pages
Squid, Varnish, ...

15. Sample architecture - 99designs.com
99designs.com

16. Cloud computing
SaaS
PaaS
IaaS

17. SaaS
Software-as-a-Service
Application hosted on the web, no installation
necessary
GMail, SalesForce, BaseCamp, thousands of others

18. PaaS
Platform-as-a-Service
No need to care about operating system etc, can
deploy your software directly, usually has good
monitoring tools
EngineYard, Heroku, AppFog, Azure Cloud, zone.
ee

19. IaaS
Infrastructure-as-a-Service
You have to deal with all the nuts and bolts
but
You get full control over your server
all Virtual Private Server providers (zone.ee,
Amazon EC2)

20. Amazon S3
Amazon Simple Storage Service
Similar services: nimbus.io, possibly others

21. CAP theorem
Consistency / Availability / Partition tolerance
Pick two

22. CAP theorem
Consistency / Availability / Partition tolerance
Pick two
Story of Remembrance, Inc

23. Optimizing and scaling up
Optimizing - making the system less resource
hungry
Scaling up - adding resources to the system

24. Optimizing and scaling up
Know what you want to improve:
page load time / throughput / server load / memory
usage

25. Optimizing and scaling up
Optimize first, then scale up
Measure first, make changes after
Identify the bottlenecks!

26. Things to do to make it better
Optimize database queries
Outsource / optimize content delivery
Introduce caching

27. Examples from
the big boys

28. Google MapReduce
Partition processing huge amounts of data (used in
search)
http://jcit.org/web/files/csc548/fpgrowth.html

29. Facebook BigPipe
Optimize page loading speed for end users
FB loads page in
blocks
https://www.facebook.com/note.php?note_id=389414033919

30. Twitter & memcached
http://www.slideshare.net/Blaine/scaling-twitter

31. Twitter & memcached
http://www.slideshare.net/Blaine/scaling-twitter

32. Twitter & memcached
Twitter does a LOT of caching: in 2007 they had
- 600 tweets/second
- 180 web servers
- 1 DB server
Can be done if you mostly read and rarely write
There are only two hard things in Computer
Science: cache invalidation and naming things.
-- Phil Karlton