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More established companies are taking advantage of the scalability of the cloud, as well. In
2011, Netflix migrated its Web site and streaming video service from a conventional datacen-
ter to AWS. Netflix's goal was to let users watch a movie on, say, their cell phone while com-
muting home and then seamlessly switch to their television when they arrive home to con-
tinue watching their movie where they left of. This effort involves batch processing to con-
vert new movies to the myriad formats they need to deliver movies on cell phones, tablets,
laptops, game consoles, and digital video recorders. These batch AWS jobs can take thousands
of machines several weeks to complete the conversions. The transactional backend for stream-
ing is done in AWS and the delivery of encoded files is done via Content Delivery Networks
such as Akamai and Level 3. The online service is much less expensive than mailing DVDs,
and the resulting low cost has made the new service popular. One study put Netflix as 30%
of Internet download traffic in the United States during peak evening periods. (In contrast,
YouTube was just 10% in the same 8 p.m. to 10 p.m. period.) In fact, the overall average is 22%
of Internet traffic, making Netflix alone responsible for the largest portion of Internet traffic in
North America. Despite accelerating growth rates in Netflix subscriber accounts, the growth
rate of Netflix's datacenter has been halted, and all capacity expansion going forward has been
done via AWS.
Cloud computing has made the benefits of WSC available to everyone. Cloud computing
offers cost associativity with the illusion of infinite scalability at no extra cost to the user: 1000
servers for 1 hour cost no more than 1 server for 1000 hours. It is up to the cloud computing
provider to ensure that there are enough servers, storage, and Internet bandwidth available
to meet the demand. The optimized supply chain mentioned above, which drops time-to-de-
livery to a week for new computers, is a considerable aid in providing that illusion without
bankrupting the provider. This transfer of risks, cost associativity, and pay-as-you-go pricing
is a powerful argument for companies of varying sizes to use cloud computing.
Two crosscuting issues that shape the cost-performance of WSCs and hence cloud comput-
ing are the WSC network and the efficiency of the server hardware and software.
6.6 Crosscutting Issues
Net gear is the SUV of the datacenter.
James Hamilton
(2009)
WSC Network As A Bottleneck
Section 6.4
showed that the networking gear above the rack switch is a significant fraction of
the cost of a WSC. Fully configured, the list price of a 128-port 1 Gbit datacenter switch from
Juniper (EX8216) is $716,000 without optical interfaces and $908,000 with them. (These list
prices are heavily discounted, but they still cost more than 50 times as much as a rack switch
did.) These switches also tend be power hungry. For example, the EX8216 consumes about
19,200 wats, which is 500 to 1000 times more than a server in a WSC. Moreover, these large
switches are manually configured and fragile at a large scale. Because of their price, it is dif-
icult to afford more than dual redundancy in a WSC using these large switches, which limits
the options for fault tolerance [
Hamilton 2009
].
However, the real impact on switches is how oversubscription affects the design of software
and the placement of services and data within the WSC. The ideal WSC network would be a
black box whose topology and bandwidth are uninteresting because there are no restrictions:
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