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<h1>Servers</h1>

<p>There are four options for setting up infrastructure to serve a

web application:</p>

<ol class="arabic simple">

<li>&quot;Bare metal&quot; servers</li>

<li>Virtualized servers</li>

<li>Infrastructure-as-a-service</li>

<li>Platform-as-a-service</li>

<div class="section" id="bare-metal">

<h2>Bare metal</h2>

<p>The term <em>bare metal</em> refers to purchasing the actual hardware and hooking

it up to the Internet either through a business-class internet service

provider (ISP) or

<a class="reference external" href="http://webdesign.about.com/od/colocation/a/what_colocation.htm">co-locating the server</a> with other servers. A &quot;business-class&quot; ISP is necessary because

most residential Internet service agreements explicitly prohibit running

web servers on their networks. You may be able to get away with low traffic

volume but if your site serves a lot of traffic it will alert an ISP's

filters.</p>

<p>The bare metal option offers the most control over the server configuration,

usually has the highest performance for the price, but also is the most

expensive upfront option and the highest ongoing maintenance. With bare

metal servers the ongoing operating cost is the electricity the server(s)

use as well as handling repairs when server components malfunction. You're

taking on manual labor working with hardware as well as the rest of the

software stack.</p>

<p>Buy actual hardware from a vendor either pre-built or as a collection of

components that you assemble yourself. Here is an

<a class="reference external" href="http://duartes.org/gustavo/blog/post/building-a-quad-core-server">example of a server buildout</a>. The post is a couple of years old but those are the

rough components you need to put together your own server. You can also buy

pre-configured servers from Dell or HP. Those servers tend to be in

smaller case form factors (called &quot;blades&quot;) but are correspondingly more

expensive than putting off-the-shelf components together yourself.</p>

<div class="section" id="virtualized-servers">

<h2>Virtualized servers</h2>

<p>Virtual private servers (VPSs) are slices of hardware on top of a larger

bare metal server. Virtualization software such as

<a class="reference external" href="http://www.xen.org/">Xen</a> and

<a class="reference external" href="http://www.vmware.com/virtualization/what-is-virtualization.html">VMWare</a>

allow providers such as <a class="reference external" href="http://www.linode.com/">Linode</a> and

<a class="reference external" href="http://prgmr.com/xen/">prgmr</a> (as well as a many others) to provide

fractions of a full server that appear as their own instances. For example,

a server with an 8-core Xeon processor and 16 gigabytes of memory can be

sliced into 8 pieces with the equivalent of 1-core and 2 gigabytes of

memory.</p>

<p>The primary disadvantage of virtualized servers is that there is resource

overhead in the virtualization process. In addition, physical constraints

such as heavy I/O operations by a single virtualized instance on persistent

storage can cause performance bottlenecks for other virtualized instances on

the shared server. Choosing virtualized server hosting should be based on

your needs for urgency of service ticket requests and the frequency you

require for ongoing maintenance such as persistent storage backups.</p>

<div class="section" id="virtualized-servers-resources">

<h2>Virtualized servers resources</h2>

<p><a class="reference external" href="http://blog.redfern.me/choosing-a-low-cost-vps/">Choosing a low cost VPS</a></p>

<div class="section" id="infrastructure-as-a-service">

<h2>Infrastructure-as-a-service</h2>

<p>Infrastructure-as-a-service (IaaS) overlaps with virtualized servers

because the resources are often presented in the same way. The

difference between virtualized servers and IaaS is the granularity of the

billing cycle. IaaS generally encourages a finer granularity based on minutes

or hours of server usage instead of on monthly billing cycles.</p>

<p>IaaS can be used in combination with virtualized servers to provide

dynamic upscaling for heavy traffic. When traffic is low then virtualized

servers can solely be used. This combination of resources reduces cost at

the expense of greater complexity in the dynamically scaled infrastructure.</p>

<p>The most common IaaS platforms are

<a class="reference external" href="http://aws.amazon.com/">Amazon Web Services</a> and

<a class="reference external" href="http://www.rackspace.com/cloud/">Rackspace Cloud</a>.</p>

<p>The disadvantage to IaaS platforms is the lock-in if you have to write

custom code to deploy, dynamically scale, and generally understand your

infrastructure. Every platform has its quirks. For example,

Amazon's standard <a class="reference external" href="http://aws.amazon.com/ebs/">Elastic Block Store</a> storage

infrastructure has at least an order of magnitude worse I/O throughput

than working with your local disk. Your application's database queries may

work great locally but then when you deploy the performance is inadequate.

Amazon has <a class="reference external" href="http://aws.amazon.com/about-aws/whats-new/2012/07/31/announcing-provisioned-iops-for-amazon-ebs/">higher throughput EBS instances</a>

but you will pay correspondingly more for them. EBS throughput is just

one of many quirks you need to understand before committing to an

IaaS platform.</p>

<div class="section" id="infrastructure-as-a-service-resources">

<h2>Infrastructure-as-a-service Resources</h2>

<p><a class="reference external" href="http://aws.amazon.com/python/">Amazon Web Services official documentation for Python</a></p>

<p><a class="reference external" href="https://github.com/boto/boto">boto</a> is an amazing Python library for

working with Amazon Web Services</p>

<p><a class="reference external" href="http://docs.rackspace.com/sdks/guide/content/python.html">Rackspace official documentation for Python</a></p>

<div class="section" id="platform-as-a-service">

<h2>Platform-as-a-service</h2>

<p>A platform-as-a-service (PaaS) provides infrastructure and a software layer

on which a web application is deployed. The PaaS layer defines how the

application accesses resources such as computing time, files, and

external services. The PaaS provides a higher-level abstraction for working

with computing resources than deploying an application to a server or IaaS.</p>

<p>A PaaS makes deployment and operations easier because it forces the developer

to conform applications to the PaaS architecture.</p>

<p><a class="reference external" href="http://www.heroku.com/">Heroku</a>,

<a class="reference external" href="https://developers.google.com/appengine/">Google App Engine</a>,

<a class="reference external" href="https://gondor.io/">Gondor</a>, and

<a class="reference external" href="https://openshift.redhat.com/community/get-started/python">OpenShift</a> are

platform-as-services that support Python web applications. Each one requires

varying tradeoffs to deploy to their respective platforms.</p>

<img alt="Traditional LAMP server stack versus a Platform-as-a-Service stack" class="technical-diagram" src="theme/img/servers-versus-paas.png" />

<p>If you go the PaaS route, you can skip over the operating system and web

server sections because they are baked into PaaS offerings. PaaS offerings

generally start at the WSGI server layer.</p>

<div class="section" id="platform-as-a-service-resources">

<h2>Platform-as-a-service resources</h2>

<p><a class="reference external" href="http://rdegges.com/devops-django-part-4-choosing-heroku">Choosing Heroku</a>

(Randall Degges)</p>

<br/>

Next read the

<a href="/operating-systems.html">operating systems</a> section.

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<a href="/introduction.html" class="list-group-item ">Introduction</a>

<a href="/servers.html" class="list-group-item active">Servers</a>

<a href="/operating-systems.html" class="list-group-item ">Operating Systems</a>

<a href="/web-servers.html" class="list-group-item ">Web Servers</a>

<a href="/databases.html" class="list-group-item ">Databases</a>

<a href="/wsgi-servers.html" class="list-group-item ">WSGI Servers</a>

<a href="/web-frameworks.html" class="list-group-item ">Web Frameworks</a>

<a href="/static-content.html" class="list-group-item ">Static Content</a>

<a href="/website-security.html" class="list-group-item ">Website Security</a>

<a href="/caching.html" class="list-group-item ">Caching</a>

<a href="/web-analytics.html" class="list-group-item ">Web Analytics</a>

<a href="/monitoring.html" class="list-group-item ">Monitoring</a>

<a href="/source-control.html" class="list-group-item ">Source Control</a>

<a href="/configuration-management.html" class="list-group-item ">Configuration Management</a>

<a href="/dependency-management.html" class="list-group-item ">Application Dependencies</a>

<a href="/no-sql-datastore.html" class="list-group-item ">NoSQL Data Stores</a>

<a href="/about-author.html" class="list-group-item ">About</a>

<a href="/change-log.html" class="list-group-item ">Change Log</a>

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