An Overview of the NoSQL World - Large Scale and Big Data: Processing and Management - page 287

end users. Finally, we present and discuss some of the current challenges and open
research problems to be tackled to improve the current state-of-the-art.
9.1 INTRODUCTION
Over the past decade, rapidly growing Internet-based services such as e-mail, blog-
ging, social networking, search, and e-commerce have substantially redefined the
way consumers communicate, access contents, share information, and purchase
products. In particular, the recent advances in the web technology have made it easy
for any user to provide and consume content of any form. For example, building a
personal web page (e.g., Google Sites*), starting a blog (e.g., WordPress, † Blogger, ‡
LiveJournal § ), and making both searchable for the public have become a commod-
ity that is available for users all over the world. Arguably, the main goal of the next
wave is to facilitate the job of implementing every application as a distributed, scal-
able, and widely accessible service on the web. Services such as Facebook, ¶ Flickr,**
YouTube, †† Zoho, ‡‡ and LinkedIn §§ are currently leading this approach. Such appli-
cations are both data-intensive and very interactive . For example, the Facebook
social network has announced that it has more than 800 millions of monthly active
users. ¶¶ Each user has an average of 130 friendship relations. Moreover, there are
about 900 million objects that registered users interact with, such as pages, groups,
events, and community pages. Other smaller scale social networks such as LinkedIn,
which is mainly used for professionals, has more than 120 million registered users.
Twitter has also claimed to have over 100 million active monthly users. Therefore, it
becomes an ultimate goal to make it easy for every application to achieve such high
scalability and availability goals with minimum efforts.
In general, relational database management systems (e.g., MySQL, PostgreSQL,
SQL Server, Oracle) have been considered as the one-size-fits-all solution for data
persistence and retrieval for decades. They have matured after extensive research
and development efforts and very successfully created a large market and solutions
in different business domains. However, the ever-increasing need for scalability and
new application requirements have created new challenges for traditional RDBMS.
Therefore, recently, there has been some dissatisfaction with this one-size-fits-all
approach in some web-scale applications [58]. Nowadays, the most common archi-
tecture to build enterprise web applications is based on a three-tier approach: the
web server layer, the application server layer, and the data layer. In practice, data
partitioning [50] and data replication [40] are two well-known strategies to achieve
the availability, scalability, and performance improvement goals in the distributed
* http://sites.google.com/.
† http://wordpress.org/.
‡ http://www.blogger.com/.
§ http://www.livejournal.com/.
¶ http://www.facebook.com/.
** http://www.flickr.com/.
†† http://www.youtube.com/.
‡‡ http://www.zoho.com/.
§§ http://www.linkedin.com/.
¶¶ http://www.facebook.com/press/info.php?statistics.