This is a presentation given on April 14, 2009 to a select group of current memcached users. It includes survey results of how the dynamic web has given rise to the distributed caching tier, describes the growing popularity of memcached, provides poll results from memcached users and offers overview of the Gear6 Web Cache solution. Gear6 will be at the 2009 MySQL Conference at booth #218. Or visit us at Gear6.com.

1. Scaling Website Performance:
Caching Session and Profile Data with Memcached
Presented by:
Joaquín Ruiz – EVP Products
Perry Krug – Systems Engineer
14 April 2009

2. About Gear6
• First and leading provider of scalable Memcached solutions
• Enabling high-growth web sites to deliver and scale dynamic
high growth
applications and content
• Memcached contributor on Github and Google Code
• Customers are leaders in media, social networking and content
aggregation
• Privately held; Headquartered in Mountain View, California
2 : Copyright 2009 Gear6 Inc.

3. The Web Has Changed
• It’s Dynamic, It’s Mobile, It’s High Speed
» Consumer internet traffic surpassed business traffic in 2008
» Dynamic (Social Aggregation Media) sites/services are the driving web growth
(Social, Aggregation,
So…
• A distributed caching tier has become necessary and ubiquitous
» Approximately 70% of websites are Linux-based (typically LAMP/Java) and are not
scalable without a distributed caching tier
Because…
• Without a distributed caching tier you have no good options
SCALE VERTICALLY: $$$ It’s very expensive to do this $$$
»
ADD LARGE AMOUNTS OF WEB, APP AND DB SERVERS: $$$ OPEX $$$
»
MOVE TO A DIFFENT STACK: “No way!
No way!”
»
GET CRUSHED/SLOW RESPONSE TIMES: “It’s gone from bad to worse”
»
“Digital Consumer – Undermonetized social networks / video / VoIP driving powerful usage
growth
growth” – Morgan Stanley Tech Research, 5 Nov 2008, Web 2.0 Summit, San Francisco
3 : Copyright 2009 Gear6 Inc.

4. Web Architecture with No Cache
Web / Application Servers
MySQL
Databases
Ad Load
Add Load
dd
d
Web / Application Servers
MySQL
Databases
Every request must hit the database servers and/or
E t t th d t b d/
re-
re-execute on application servers
4 : Copyright 2009 Gear6 Inc.

5. Memcached to the Rescue
• Memcached: a distributed memory object caching system intended
for use in speeding up dynamic web applications by alleviating
database load
• Memcached is an open source project that developed around the
need for dynamic web sites to have a distributed caching tier
» Technology: Memcached is a generic two stage hashing system (clients and
servers). Clients are written for specific application languages. Server is
written in C
» U cases: HTML MySQL, Session/profile caching
Use HTML, M SQL S i/ fil hi
• Memcached is de facto solution
» 85% of top 20 sites use memcached; 50%+ of top 5k sites uses Memcached
» Memcached has client libraries in all major languages
» Memcached has application level plug-ins for apps like WordPress and
Drupal
5 : Copyright 2009 Gear6 Inc.

6. Why should I use Memcache?
• Enables scale-out of dynamic websites
• Faster page loads
pg
• Allows for efficient use of your database
• Can utilize existing network infrastructure
• Very flexible – architect for your workload & resources
6 : Copyright 2009 Gear6 Inc.

7. Web Architecture with Memcached
Web / Application Servers
Without Memcached
MySQL
Databases
Web / Application Servers
With Memcached
Perfect for
dynamic website
Memcached
that generate a
Memcache Server(s)
e cac ed
Memcached
high load on their
hi h l d th i
MySQL
Memcached database
Databases
7 : Copyright 2009 Gear6 Inc.

8. Challenges of Memcached
Challenges:
» Many web implementations require lots of
memory and lots of servers for memcache:
• Ad i i t ti
Administration, power, cooling and
li d
rackspace challenge
» No built-in failover or replication
» Instances managed individually
• Lack of consolidated management and
aggregated statistic gathering
• Can be challenging to troubleshoot client,
service, instance and key relationships
Source: “MySQL and memcached” May 2008 seminar
8 : Copyright 2009 Gear6 Inc.

9. What is a Session?
• Al
Almost always l
tl larger th
than 250 b t
bytes, and almost
dl t
always smaller than 5 kilobytes
• Read from datastore for every logged in user for
every dynamic page load
• Written to the datastore for every dynamic page
load
• Eventually reaped from the database after N
minutes of inactivity
Credits: “Cache your sessions. Don't piss off your users” by Dormando
9 : Copyright 2009 Gear6 Inc.

10. Example: Scaling the User Profile
• Too many users creates a load on the database
• Replicating the database will help this
p g p
» Will quickly experience DB replication lag
Source: “”Scaling and Tuning MySQL.com” Jan 2009
10 : Copyright 2009 Gear6 Inc.

11. Where do you keep your Sessions?
• Bad: Local sessions (on disk or in memory)
» Can’t move users
Can t
» Can’t avoid hotspots
» Not fault tolerant
• Good: Centralized sessions (in a central
database or in-memory)
in memor )
» No porting around of session data
» No need for sticky sessions
» No hot spots
Credits: “Scalable Web Architectures” by Cal Henderson
11 : Copyright 2009 Gear6 Inc.

12. Caching Sessions with Memcached
• Common Wisdom: You Don’t
» Users will get logged out if anything goes wrong with
memcached
» Evictions means that people are logged out of your site
» If you upgrade memcached, OS, hardware etc., everyone will
be logged off
» Addi /
Adding/removing memcached servers ki k people off site
i hd kicks l ff it
• BUT the benefit of caching sessions is HUGE
» It is VERY FAST - Zero reads or writes to the database
… so people do!
Credits: “Cache your sessions. Don't piss off your users” by Dormando
12 : Copyright 2009 Gear6 Inc.

13. Session Caching Options
Approach 1:
» Memcached / MySQL hybrid ! Run batch/cron jobs to store session data in
both database and memcached
» Good for smaller sites or sites where it doesn’t matter as much if session
data is lost
(Gear6 Approach):
Approach 2
» Store session in memcached space only
» Provide sufficient memory space to eliminate evictions
• Leverage flash density to reduce space and costs
• Use DRAM to provide low latency
» Use server-based replication to eliminate memcached misses
b d l l hd
13 : Copyright 2009 Gear6 Inc.

14. Gear6: Session Caching Customer Case
Production Customer Stats:
Alexa rank: top 150 worldwide
»
10’s of millions of page views per day
»
28 million unique users per month in 2008
»
Previously used memcached v 1.2.6 to cache sessions
»
About 120GB of memcache data used
»
Customer challenges:
g
» Need to provide very fast access to use profile information in order
to present user with appropriate content (based on user ratings)
» Customer: rack space limited and cost sensitive
» Need to increase administrative efficiency for memcached tier
» Memcached reload can take several hours if failure occurs during
which DB load is very high and service latency increased
14 : Copyright 2009 Gear6 Inc.

15. Gear6: Session Caching Customer Case
• Without Gear6:
Zero High Availability / Redundancy
Slower user experience
»
4 U rack space
»
~800W power consumption
800W
»
Zero configuration management
»
Minimal statistics (Cacti)
»
Cost per Gig = $100 for hardware only
»
Double everything for redundancy
32GB 32GB 32GB 32GB
15 : Copyright 2009 Gear6 Inc.

16. Gear6: Session Caching Customer Case
• With Gear6:
Fully redundant / cache data protection
y p
» 2 U rack space
» ~400W power consumption
» Single point for management
gp g
» Enhanced stream analysis and statistics
» Cost per Gig = $70 for entire solution
Savings & benefits of Gear6 solution vs. without Gear6:
Over $8k/year in power savings
»
Immediately deployable with no code changes
»
1/4th the rack space
»
Customers immediately presented with high-affinity content based
»
on profile and rating history
p g y
» Less expensive to deploy with Gear6 than without!
16 : Copyright 2009 Gear6 Inc.

17. Gear6 Web Cache Specifications
Gear6 Web Cache Software Gear6 Web Cache Module
• High memory density &
advance memory allocation
» Best-in-class hybrid RAM-Flash
Best in class RAM Flash
configurations
» Advanced memory management
» Most efficient object eviction implementation
Gear6 software delivered on best-of-breed,
» High bandwidth support industry standard servers, DRAM and Flash
• High availability
Module specs:
» Rich cluster functionality
•1 U rack profile with four flash drive bays
» Failover configurations
•Minimum of two modules per appliance
» Cache replication options
•Two power supplies per module
• Advanced management •Four bonded GE ports per module
» Hot key and client analysis •Two Quad Core processors
» Service-wide diagnostics •Up to 300GB per rack unit
» Aggregated physical and logical views
17 : Copyright 2009 Gear6 Inc.

18. Resources
• www.gear6.com
• Twitter
» twitter.com/memcached
• Github
» http://github.com/zyounker/brutis/tree/master
p //g /y / / /
» http://github.com/rama/statsproxy/tree/master
• Google code
» http://code.google.com/p/brutis/wiki/Readme
» http://code.google.com/p/statsproxy/
18 : Copyright 2009 Gear6 Inc.

19. April 14, 2009 Webinar Poll Results
If you do use memcached, do you use it for:
None of the above 0%
All of the above 8%
Session and profile caching 0%
Caching HTML web pages 42%
MySQL or other data caching 67%
What client are you using for memcached?
Other 44%
Perl 0%
Java Based 11%
PHP 44%
19 : Copyright 2009 Gear6 Inc.

20. Questions?
Thank you for attending
“Scaling Website Performance: Caching Session and
Profile D
P fil Data with Memcached”
ihM h d”
presented by Gear6
Joaquin Ruiz
Gear6
salesinfo@gear6.com
+1 650 587 7116
20 : Copyright 2009 Gear6 Inc.