This document discusses scalability concepts and practices. It provides examples of how LiveJournal scaled their infrastructure from 1 server to 45 servers by adding more hardware resources like CPUs and databases, and software solutions like caching and load balancing. The key lessons are that using multiple scalability solutions intelligently is best, hardware will likely need to be added, and system knowledge is important to understand bottlenecks. The goal of scaling is to allow for easy growth.

1. Scalability: Concepts and
Practices
Danny DiPaolo
June 16, 2009
Pariveda Lightning Lunch #8

2. Why scale?
• Speed
• Reliability
• Ease of growth

3. How do you scale?
• Hardware
– Throwing more CPU, hard drive, network speed,
etc. at the problem
• Software
– Implementing caching solutions, reducing
overhead, tweaking algorithms, partitioning
• Infrastructure
– Vertical/horizontal scaling

4. Example: livejournal
1. 1 server: web + database
2. 2 servers: web, database
3. 4 servers: 3 web, database
4. 5 servers: 3 web, 2 database
5. <skip a few>
6. 24 servers: 2 lb’s, 3 gateways, 12 web, 1 master db, 6
slave db
7. 45 servers: 2 lb’s, 5 gateways, 25 web, 1 global db
master, 2 db cluster masters, 10 db slaves (6, 2, 2)
http://danga.com/words/2005_oscon/oscon-2005.pdf

5. Example: livejournal (cont’d)
• Didn’t even get into:
– Caching (memcached)
– Custom FS (MogileFS)
– Custom load-balancing (Perlbal)

6. Lessons learned
• Using any of the one scaling solutions will
help, but using them all intelligently will help
more
• If you need to scale, chances are you will have
to throw new hardware at the problem
• Need good system knowledge to understand
bottlenecks and points of failure
• The goal:

7. The goal

8. References
• Livejournal scalability:
http://danga.com/words/2005_oscon/oscon-2005.pdf
• Flickr + MySQL: http://www.scribd.com/doc/21793/Scaling-
PHPMySQL-Presentation-from-Flickr
• Youtube + MySQL:
http://itc.conversationsnetwork.org/shows/detail3299.html
• Flickr architecture:
http://www.bytebot.net/blog/archives/2007/04/25/federati
on-at-flickr-a-tour-of-the-flickr-architecture
• Facebook engineering notes:
http://www.facebook.com/notes.php?id=9445547199

9. Questions?
• Danny DiPaolo
• Email: danny.dipaolo@parivedasolutions.com
• Gtalk: ddipaolo@gmail.com
• Twitter: @ddipaolo
• LinkedIn:
http://www.linkedin.com/in/ddipaolo