We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
from VI - Real-World Workloads: High Variability and Heavy Tails
Published online by Cambridge University Press: 05 February 2013
In this chapter we revisit server farms, however this time in the context of high-variability job sizes (indicative of the workloads described in Chapter 20), rather than Exponential job sizes.
The server farm architecture is ubiquitous in computer systems. Rather than using a single, powerful server to handle all incoming requests (assuming such a beast can even be purchased), it is more cost efficient to buy many slow, inexpensive servers and pool them together to harness their combined computational power. The server farm architecture is also popular for its flexibility: It is easy to add servers when load increases and easy to take away servers when the load drops. The term server farm is used to connote the fact that the servers tend to be co-located, in the same room or even on one rack.
Thus far, we have primarily studied server farms with a central queue, as in the M/M/k system, which we initially examined in Chapter 14 and then revisited from a capacity provisioning perspective in Chapter 15. In the M/M/k, jobs are held in a central queue, and only when a server is free does it take on the job at the head of the queue.
By contrast, in computer systems, most server farms do immediate dispatching (also known as task assignment), whereby incoming jobs are immediately assigned to servers (also known as hosts). There is typically no central queue; instead the queues are at the individual hosts.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.
