Clean up tech_considerations_hybrid.xml
Change-Id: Ib230052311f0f94045b73556aae945ba195137f8 Implements: blueprint arch-guide
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Brian Moss
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<?dbhtml stop-chunking?>
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<title>Technical considerations</title>
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<para>A hybrid cloud environment requires inspection and
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understanding of technical issues that are not only outside of
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an organization's data center, but potentially outside of an
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organization's control. In many cases, it is necessary to
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ensure that the architecture and CMP chosen are adaptable.
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All of these factors influence
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and add complexity to the design of the hybrid cloud architecture.</para>
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<para>Incompatibilities with other cloud platforms are inevitable,
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however, clouds using the same version and distribution
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of OpenStack are unlikely to experience any issues.</para>
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understanding of technical issues in external data centers that may
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not be in your control. Ideally, select an architecture
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and CMP that are adaptable to changing environments.</para>
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<para>Using diverse cloud platforms increases the risk of compatibility
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issues, but clouds using the same version and distribution
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of OpenStack are less likely to experience problems.</para>
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<para>Clouds that exclusively use the same versions of OpenStack should
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have no issues, regardless of distribution. The newer the distribution in
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question, the less likely it is that there will be
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incompatibilities between versions. An OpenStack community initiative defines
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core functions that need to remain backward compatible between supported
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versions.</para>
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<note>
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<para>For example, the DefCore initiative defines
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basic functions that every distribution must support in order
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to bear the name <productname>OpenStack</productname>.</para>
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</note>
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have no issues, regardless of distribution. More recent distributions
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are less likely to encounter incompatibility between versions. An
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OpenStack community initiative defines core functions that need to
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remain backward compatible between supported versions. For example, the
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DefCore initiative defines basic functions that every distribution must
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support in order to use the name <productname>OpenStack</productname>.
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</para>
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<para>Vendors can add proprietary customization to their distributions. If
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an application or architecture makes use of these features, it will be
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an application or architecture makes use of these features, it can be
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difficult to migrate to or use other types of environments.</para>
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<para>If an environment includes non-OpenStack clouds, it may experience
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compatibility problems. CMP tools must account for the differences in the
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handling of operations and implementation of services. Some situations in which these
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incompatibilities can arise include differences between the way in which a
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cloud:</para>
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compatibility problems. CMP tools must account for the differences in
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the handling of operations and the implementation of services.</para>
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<itemizedlist>
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<title>Possible cloud incompatibilities</title>
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<listitem>
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<para>Deploys instances</para>
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<para>Instance deployment</para>
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</listitem>
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<listitem>
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<para>Manages networks</para>
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<para>Network management</para>
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</listitem>
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<listitem>
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<para>Treats applications</para>
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<para>Application management</para>
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</listitem>
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<listitem>
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<para>Implements services</para>
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<para>Services implementation</para>
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</listitem>
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</itemizedlist>
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<section xml:id="capacity-planning-hybrid">
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<title>Capacity planning</title>
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<para>One of the primary reasons many organizations turn to a
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hybrid cloud system is to increase capacity without having to
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make large capital investments.</para>
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<para>Capacity, and the placement of workloads,
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accounts for the design of a mostly
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internally-operated cloud.
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The long-term capacity plan for this design must incorporate
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growth over time to prevent permanent consumption of a more
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expensive external cloud. In order to avoid this scenario, we
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recommend accounting for the future applications' capacity
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requirements and plan growth appropriately.</para>
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<para>Unpredictability is a consideration for capacity planning. It is
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difficult to predict the amount of load a particular application
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might incur if the number of users fluctuate, or the application
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experiences an unexpected increase in popularity. It is possible
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to define application requirements in terms of vCPU, RAM, bandwidth
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or other resources and plan appropriately. However, other clouds
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might not use the same meter or even the same oversubscription rates.</para>
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<para>One of the primary reasons many organizations use a
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hybrid cloud is to increase capacity without making large capital
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investments.</para>
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<para>Capacity and the placement of workloads are key design considerations
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for hybrid clouds. The long-term capacity plan for these
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designs must incorporate growth over time to prevent permanent
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consumption of more expensive external clouds. To avoid this scenario,
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account for future applications' capacity requirements and plan growth
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appropriately.</para>
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<para>It is difficult to predict the amount of load a particular
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application might incur if the number of users fluctuates, or the
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application experiences an unexpected increase in use. It is
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possible to define application requirements in terms of vCPU, RAM,
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bandwidth, or other resources and plan appropriately. However, other
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clouds might not use the same meter or even the same oversubscription
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rates.</para>
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<para>Oversubscription is a method to emulate more capacity than
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may physically be present. For example, a physical
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hypervisor node with 32 GB RAM may host 24
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instances, each provisioned with 2 GB RAM. As long
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as all 24 instances are not concurrently utilizing 2 full
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gigabytes, this arrangement is a non-issue. However, some
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as all 24 instances do not concurrently use 2 full
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gigabytes, this arrangement works well. However, some
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hosts take oversubscription to extremes and, as a result,
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performance can frequently be inconsistent. If at all
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performance can be inconsistent. If at all
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possible, determine what the oversubscription rates of each
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host are and plan capacity accordingly.</para>
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</section>
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<section xml:id="security-hybrid">
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<title>Security</title>
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<para>Security domains are an important distinction when planning for a hybrid
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cloud environment and its capabilities. A security domain
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comprises users, applications, servers or networks that share
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common trust requirements and expectations within a
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system.</para>
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<para>The security domains are:</para>
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<orderedlist>
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<listitem>
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<para>Public</para>
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</listitem>
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<listitem>
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<para>Guest</para>
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</listitem>
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<listitem>
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<para>Management</para>
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</listitem>
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<listitem>
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<para>Data</para>
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</listitem>
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</orderedlist>
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<para>You can map the security domains individually to the
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organization's installation or combine them. For example, some
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deployment topologies combine both guest and data domains onto
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one physical network, whereas other topologies physically
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separate the networks. In each case, the cloud operator
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should be aware of the appropriate security concerns. We recommend
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mapping security domains against the specific OpenStack
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deployment topology. The domains and their trust requirements
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depend upon whether the cloud instance is public, private, or
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hybrid.</para>
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<para>The public security domain is an entirely untrusted area of
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the cloud infrastructure. It can refer to the internet as a
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whole, or simply to networks over which an organization has no
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authority. Do not trust this domain.
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For example, in a hybrid cloud deployment, any information traversing
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between and beyond the clouds is of the public domain and untrustworthy.</para>
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<para>The guest security domain handles compute
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data. Instances on the cloud generate the data, but not services that
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support the operation of the cloud, such as API calls. We recommend not
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to trust this domain if you are a public cloud provider that
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uses hybrid cloud configurations, or a private cloud provider who does
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not have controls on instance use and allows unrestricted internet access
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to instances. Private cloud providers, however, can use this network as
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an internally trusted network if controls are in place.</para>
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<para>The management security domain is where services interact.
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The networks in this domain transport confidential data such as configuration
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parameters, user names, and passwords. Trust this domain when it is
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behind an organization's firewall in deployments.</para>
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<para>The data security domain is concerned primarily with
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information pertaining to the storage services within
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OpenStack. The data that crosses this network has integrity and
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confidentiality requirements. Depending on the type of deployment there
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may also be availability requirements. The trust level of this network
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is heavily dependent on deployment decisions and does not have a default
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level of trust.</para>
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<para>When operating or utilizing public or private clouds, consider the management
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of the users. The identity service allows for LDAP to be part of the
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authentication process. Including these systems in your
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OpenStack deployments may ease user management if integrating
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into existing systems.</para>
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<warning>
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<para>Be mindful of consistency when utilizing third party
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clouds to explore authentication options.</para>
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</warning>
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<para>Due to the passing of user names, passwords, and tokens between
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client machines and API endpoints, we recommend the placement of API
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services behind hardware to perform SSL termination.</para>
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<para>The hypervisor also requires a security assessment. In a public cloud,
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organizations typically do not have control over the choice of
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hypervisor. For example, Amazon uses its own particular version of Xen.
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Properly securing your hypervisor is important. Attacks made upon the
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unsecured hypervisor are called a "hypervisor breakout".
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Hypervisor breakout describes the event of a
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compromised or malicious instance breaking out of the resource
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controls of the hypervisor and gaining access to the bare
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metal operating system and hardware resources.</para>
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<para>There is not an issue if the security of instances is not important.
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However, enterprises need to avoid vulnerability. The only way to
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do this is to avoid the situation where the instances are running
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on a public cloud. That does not mean that there is a
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need to own all of the infrastructure on which an OpenStack
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installation operates; it suggests avoiding situations in which
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sharing hardware with others occurs.</para>
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<para>There are other services worth considering that provide a
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bare metal instance instead of a cloud. In other cases, it is
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possible to replicate a second private cloud by integrating
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with a private Cloud-as-a-Service deployment. The
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organization does not buy the hardware, but also does not share
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with other tenants. It is also possible to use a provider that
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hosts a bare-metal "public" cloud instance for which the
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hardware is dedicated only to one customer, or a provider that
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offers private Cloud-as-a-Service.</para>
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<para>It is important to realize that each cloud
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implements services differently. What keeps data secure in one
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cloud may not do the same in another. Be sure to know the
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security requirements of every cloud that handles the
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organization's data or workloads.</para>
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<para>More information on OpenStack Security can be found in the
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<link
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xlink:href="http://docs.openstack.org/security-guide"><citetitle>OpenStack
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Security Guide</citetitle></link>.
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</para>
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</section>
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<section xml:id="utilization-hybrid">
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<title>Utilization</title>
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<para>When it comes to utilization, it is important that the CMP
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understands what workloads are running, where they are
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<para>A CMP must be aware of what workloads are running, where they are
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running, and their preferred utilizations. For example, in
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most cases it is desirable to run as many workloads internally
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as possible, utilizing other resources only when necessary. On
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the other hand, situations exist in which the opposite is
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true. The internal cloud may only be for development and
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stressing it is undesirable. In most cases, a cost model of
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various scenarios helps with this decision. However, internal
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priorities influence this analysis. To improve efficiency,
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make these decisions programmatically.</para>
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<para>The Telemetry module (ceilometer)
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provides information on the usage of various OpenStack
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components. There are two limitations to consider:</para>
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true, such as when an internal cloud is only for development and
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stressing it is undesirable. A cost model of various scenarios and
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consideration of internal priorities helps with this decision. To
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improve efficiency, automate these decisions when possible.</para>
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<para>The Telemetry module (ceilometer) provides information on the usage
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of various OpenStack components. Note the following:</para>
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<itemizedlist>
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<listitem>
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<para>
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If there is to be a large amount of data (for example, if
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monitoring a large cloud, or a very active one) it is
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desirable to use a NoSQL back end for Ceilometer, such as
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MongoDB.</para>
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If Telemetry must retain a large amount of data, for
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example when monitoring a large or active cloud, we recommend
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using a NoSQL back end such as MongoDB.</para>
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</listitem>
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<listitem>
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<para>
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@ -226,96 +106,91 @@
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<section xml:id="performance-hybrid">
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<title>Performance</title>
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<para>Performance is of the upmost importance in the design of a
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cloud. When it comes to a hybrid cloud deployment, many of the
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same issues for multi-site deployments apply, such as network
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latency between sites. It is also important to think about the
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speed at which a workload can be spun up in another cloud, and
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how to reduce the time necessary to accomplish the task.
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This may mean moving data closer to applications
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or applications closer to the data they process, including a
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<para>Performance is critical to hybrid cloud deployments, and they are
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affected by many of the same issues as multi-site deployments,
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such as network latency between sites. Also consider the time required
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to run a workload in different clouds and methods for reducing this
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time. This may require moving data closer to applications
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or applications closer to the data they process, and
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grouping functionality so that connections that
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require low latency take place over a single cloud rather than
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spanning clouds. This may also mean ensuring that the CMP has
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the intelligence to know which cloud can most efficiently run
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which types of workloads.</para>
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<para>As with utilization, native OpenStack tools are available to
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assist. Ceilometer can measure performance and, if necessary,
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the Orchestration (heat) module can
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react to changes in demand by spinning up more resources.</para>
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spanning clouds. This may also require a CMP that can determine which
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cloud can most efficiently run which types of workloads.</para>
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<para>As with utilization, native OpenStack tools help improve performance.
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For example, you can use Telemetry to measure performance and the
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Orchestration module (heat) to react to changes in demand.</para>
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<note>
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<para>It is important to note, however, that Orchestration requires
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special configurations in the client to enable functioning
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with solution offerings from Amazon Web Services. When dealing
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with other types of clouds, it is necessary to rely on the
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features of the CMP.
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<para>Orchestration requires special client configurations to integrate
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with Amazon Web Services. For other types of clouds, use CMP
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features.
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</para>
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</note>
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</section>
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<section xml:id="components">
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<title>Components</title>
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<para>The number and types of native OpenStack components that are
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available for use is dependent on whether the deployment is
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exclusively an OpenStack cloud or not.</para>
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<para>Using more than one cloud in any situation requires
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consideration of four OpenStack tools:</para>
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<itemizedlist>
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<para>Using more than one cloud in any design requires consideration of
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four OpenStack tools:</para>
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<variablelist>
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<varlistentry>
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<term>OpenStack Compute (nova)</term>
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<listitem>
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<para>OpenStack Compute (nova): Regardless of deployment
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location, hypervisor choice has a direct effect on how
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difficult it is to integrate with one or more
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additional clouds. For example, integrating a Hyper-V
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based OpenStack cloud with Azure has less
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compatibility issues than if KVM is used.</para>
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<para>Regardless of deployment location, hypervisor choice has a
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direct effect on how difficult it is to integrate with
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additional clouds.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Networking (neutron)</term>
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<listitem>
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<para>Networking (neutron): Whether OpenStack Networking
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or legacy networking (nova-network) is used, the network is one place
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where understanding integration capabilities is necessary
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in order to connect between clouds.</para>
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<para>Whether using OpenStack Networking (neutron) or legacy
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networking (nova-network), it is necessary to understand
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network integration capabilities in order to
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connect between clouds.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Telemetry module (ceilometer)</term>
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<listitem>
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<para>Telemetry module (ceilometer): Use of Telemetry
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depends, in large part, on what the other parts of the
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cloud are using.</para>
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<para>Use of Telemetry depends, in large part, on what the other
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parts of the cloud you are using.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Orchestration module (heat)</term>
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<listitem>
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<para>Orchestration module (heat): Similarly, Orchestration can
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be a valuable tool in orchestrating tasks a CMP
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decides are necessary in an OpenStack-based
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cloud.</para>
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<para>Orchestration can be a valuable tool in orchestrating tasks a
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CMP decides are necessary in an OpenStack-based cloud.</para>
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</listitem>
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</itemizedlist>
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</varlistentry>
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</variablelist>
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</section>
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<section xml:id="special-considerations-hybrid">
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<title>Special considerations</title>
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<para>Hybrid cloud deployments also involve two more issues that
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<para>Hybrid cloud deployments require consideration of two issues that
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are not common in other situations:</para>
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<itemizedlist>
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<variablelist>
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<varlistentry>
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<term>Image portability</term>
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<listitem>
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<para>Image portability: Note that, as of the Kilo release,
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there is no single common image format that is usable by all
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clouds. Conversion or the recreation of images is necessary
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if porting between clouds. To make things simpler,
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launch the smallest and simplest images feasible, installing
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only what is necessary preferably using a deployment manager
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such as Chef or Puppet. Do not use golden images for speeding up
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the process. However, if you repeat the deployment of the same
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images, we recommend utilizing this technique instead of provisioning
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applications on lighter images each time.</para>
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<para>As of the Kilo release, there is no common image format that is
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usable by all clouds. Conversion or recreation of images is necessary
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if migrating between clouds. To simplify deployment, use the smallest
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and simplest images feasible, install only what is necessary, and
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use a deployment manager such as Chef or Puppet. Do not use golden
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images to speed up the process unless you repeatedly deploy the same
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images on the same cloud.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>API differences</term>
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<listitem>
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<para>API differences: Avoid using a hybrid cloud deployment with more than
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just OpenStack (or with different versions of OpenStack).
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The APIs need to perform certain functions that are different.
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The CMP needs to know how to handle all necessary
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versions. To get around this issue, some implementers build
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portals to achieve a hybrid cloud environment, but a heavily
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developer-focused organization may benefit more from a hybrid
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cloud broker SDK such as jClouds.</para>
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<para>Avoid using a hybrid cloud deployment with more than just
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OpenStack (or with different versions of OpenStack) as API changes
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can cause compatibility issues.</para>
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</listitem>
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</itemizedlist>
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</varlistentry>
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</variablelist>
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</section>
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</section>
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