Page 240 - Using MIS

208 Chapter 6 The Cloud

ahead of time, if there will be a thousand, or a million, or ten million, or even more site visits.
Further, the ad may appeal more to one nationality than to another. Will 70 percent of those
visits arise in the United States and the rest in Europe? Or will there be millions from Japan?
Or Australia? Given this uncertainty, how does Allroad prepare its computing infrastructure?
AllRoad knows that if it cannot provide very short response time (say, a fraction of a second), it
will lose the benefit of an incredibly expensive ad. On the other hand, if the ad is a flop, prepro-
visioning of thousands of servers will add to the accumulation of wasted money.
Figure 6-1 shows an example of this situation, based on a real case supported by Amazon.
com’s CloudFront (see Q4). Suppose Figure 6-1 shows the processing on AllRoad Parts’ Web site
during the Academy Awards. Throughout the day, AllRoad is delivering less than 10 Gbps of its
content to users. However, as soon as its ad runs (2 PM in this time zone), demand increases seven-
fold and stays high for half an hour. After the announcement of Best Picture, when its ad runs again,
demand again increases to 30 and 40 Gpbs for an hour and then returns to its base level.
Without an increase in servers, response time will be 3 or 5 seconds or more, which is far too
long to maintain the attention of a charged-up Academy Awards viewer. However, AllRoad has con-
tracted with its cloud vendor to add servers, wherever needed worldwide, to keep response time to
less than 0.5 seconds. Using cloud technology, the cloud vendor will programmatically increase its
servers to keep response time below the 0.5-second threshold. As demand falls after the ad runs a
second time, it will release the excess servers and reallocate them at the end of the awards.
In this way, AllRoad need not build or contract for infrastructure that supports maximum
demand. Had it done so, the vast majority of its servers would have been idle for most of the eve-
ning. And, as you’ll learn, the cloud vendor can provision servers worldwide using the cloud; if a
good portion of the excess demand is in Singapore, for example, it can provision extra servers in
Asia and reduce wait time due to global transmission delays.

Pooled

The second key in the definition of cloud is pooled. Cloud resources are pooled because many
different organizations use the same physical hardware; they share that hardware through virtu-
alization. Cloud vendors dynamically allocate virtual machines to physical hardware as customer
needs increase or decrease. Thus, servers that advertisers need for the Academy Awards can be re-
allocated to CPA firms that need them later that same day, to textbook publishers who need them
for online student activity on Monday, or to the hotel industry that needs them later the next week.
An easy way to understand the essence of this development is to consider electrical power.
In the very earliest days of electric power generation, organizations operated their own gen-
erators to create power for their company’s needs. Over time, as the power grid expanded, it
became possible to centralize power generation so that organizations could purchase just the
electricity they needed from an electric utility.

Need: Scalability
80
70 Peak usage over 60 Gbps
Volume of Data Delivered (Gbps) 50
60

40
30
20
10
Figure 6-1 0
Example Video Banner 8.00 AM 9.00 AM 10.00 AM 11.00 AM 12.00 PM 1.00 PM 2.00 PM 3.00 PM 4.00 PM 5.00 PM 6.00 PM 7.00 PM 8.00 PM 9.00 PM
Example: Video banner ad customer
Ad Customer