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Removal of passive voice from section_tech_considerations

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doc/arch-design/generalpurpose/section_tech_considerations_general_purpose.xml
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@ -10,48 +10,71 @@
xml:id="technical-considerations-general-purpose">
<?dbhtml stop-chunking?>
<title>Technical considerations</title>
<para>When designing a general purpose cloud, there is an implied
requirement to design for all of the base services generally
associated with providing Infrastructure-as-a-Service:
compute, network and storage. Each of these services have
different resource requirements. As a result, it is important
to make design decisions relating directly to the service
currently under design, while providing a balanced
infrastructure that provides for all services.</para>
<para>When designing an OpenStack cloud as a general purpose
cloud, the hardware selection process can be lengthy and
involved due to the sheer mass of services which need to be
designed and the unique characteristics and requirements of
each service within the cloud. Hardware designs need to be
generated for each type of resource pool; specifically,
compute, network, and storage. In addition to the hardware
designs, which affect the resource nodes themselves, there are
also a number of additional hardware decisions to be made
related to network architecture and facilities planning. These
factors play heavily into the overall architecture of an
OpenStack cloud.</para>
<para>General purpose clouds are often expected to
include these base services:</para>
<itemizedlist>
<listitem>
<para>
Compute
</para>
</listitem>
<listitem>
<para>
Network
</para>
</listitem>
<listitem>
<para>
Storage
</para>
</listitem>
</itemizedlist>
<para>Each of these services has different resource requirements.
As a result, you must make design decisions relating directly
to the service, as well as provide a balanced infrastructure for all services.</para>
<para>Consider the unique aspects of each service that requires design since
individual characteristics and service mass can impact the hardware selection
process. Hardware designs are generated for each type of the
following resource pools:</para>
<itemizedlist>
<listitem>
<para>
Compute
</para>
</listitem>
<listitem>
<para>
Network
</para>
</listitem>
<listitem>
<para>
Storage
</para>
</listitem>
</itemizedlist>
<para>Hardware decisions are also made in relation to network architecture
and facilities planning. These factors play heavily into
the overall architecture of an OpenStack cloud.</para>
<section xml:id="designing-compute-resources-tech-considerations">
<title>Designing compute resources</title>
<para>We recommend you design compute resources as pools of
resources which will be addressed on-demand. When designing
compute resource pools, a number of factors impact your design
decisions. For example, decisions related to processors,
memory, and storage within each hypervisor are just one
element of designing compute resources. In addition, it is
necessary to decide whether compute resources will be provided
in a single pool or in multiple pools.</para>
<para>To design for the best use of available resources by
applications running in the cloud, we recommend you design
more than one compute resource pool. Each independent resource
pool should be designed to provide service for specific
flavors of instances or groupings of flavors. For the purpose
of this book, "instance" refers to a virtual machine and the
operating system running on the virtual machine. Designing
multiple resource pools helps to ensure that, as instances are
<title>Designing compute resources</title>
<para>When designing compute resource pools, a number of factors
can impact your design decisions.
For example, decisions related to processors, memory, and
storage within each hypervisor are just one element of designing
compute resources. In addition, decide whether to provide compute
resources in a single pool or in multiple pools.
We recommend the compute design allocates multiple pools of resources to
be addressed on-demand.</para>
<para>A compute design that allocates multiple pools of resources makes best
use of application resources running in the cloud.
Each independent resource pool should be designed to provide service for specific
flavors of instances or groupings of flavors.
Designing multiple resource pools helps to ensure that, as instances are
scheduled onto compute hypervisors, each independent node's
resources will be allocated in a way that makes the most
efficient use of available hardware. This is commonly referred
to as bin packing.</para>
resources will be allocated to make the most efficient use of available
hardware. This is commonly referred to as bin packing.</para>
<para>Using a consistent hardware design among the nodes that are
placed within a resource pool also helps support bin packing.
Hardware nodes selected for being a part of a compute resource
@ -59,15 +82,14 @@
layout. By choosing a common hardware design, it becomes
easier to deploy, support and maintain those nodes throughout
their life cycle in the cloud.</para>
<para>OpenStack provides the ability to configure overcommit
ratio&mdash;the ratio of virtual resources available for allocation
to physical resources present&mdash;for both CPU and memory. The
default CPU overcommit ratio is 16:1 and the default memory
overcommit ratio is 1.5:1. Determine the tuning of the
overcommit ratios for both of these options during the design
phase, as this has a direct impact on the hardware layout of
your compute nodes.</para>
<para>As an example, consider that a m1.small instance uses 1
<para>An <firstterm>overcommit ratio</firstterm> is the ratio of available
virtual resources, compared to the available physical resources.
OpenStack is able to configure the overcommit ratio for CPU and memory.
The default CPU overcommit ratio is 16:1 and the default memory
overcommit ratio is 1.5:1. Determining the tuning of the overcommit
ratios for both of these options during the design phase is important
as it has a direct impact on the hardware layout of your compute nodes.</para>
<para>For example, consider a m1.small instance uses 1
vCPU, 20&nbsp;GB of ephemeral storage and 2,048&nbsp;MB of RAM. When
designing a hardware node as a compute resource pool to
service instances, take into consideration the number of
@ -83,77 +105,97 @@
required to service operating system and service needs.</para>
<para>Processor selection is an extremely important consideration
in hardware design, especially when comparing the features and
performance characteristics of different processors. Some
newly released processors include features specific to
virtualized compute hosts including hardware assisted
virtualization and technology related to memory paging (also
known as EPT shadowing). These features have a tremendous
positive impact on the performance of virtual machines running
in the cloud.</para>
<para>In addition to the impact on actual compute services, it is
also important to consider the compute requirements of
performance characteristics of different processors. Processors
can include features specific to virtualized compute hosts including
hardware assisted virtualization and technology related to memory paging (also
known as EPT shadowing). These types of features can have a significant impact on the
performance of your virtual machine running in the cloud.</para>
<para>It is also important to consider the compute requirements of
resource nodes within the cloud. Resource nodes refer to
non-hypervisor nodes providing controller, object storage,
block storage, or networking services in the cloud. The number
of processor cores and threads has a direct correlation to the
non-hypervisor nodes providing the following in the cloud:</para>
<itemizedlist>
<listitem>
<para>
Controller
</para>
</listitem>
<listitem>
<para>
Object storage
</para>
</listitem>
<listitem>
<para>
Block storage
</para>
</listitem>
<listitem>
<para>
Networking services
</para>
</listitem>
</itemizedlist>
<para>The number of processor cores and threads has a direct correlation to the
number of worker threads which can be run on a resource node.
It is important to ensure sufficient compute capacity and
memory is planned on resource nodes.</para>
As a result, you must make design decisions relating directly to
the service, as well as provide a balanced infrastructure for all services.</para>
<para>Workload profiles are unpredictable in a general purpose
cloud, so it may be difficult to design for every specific use
case in mind. Additional compute resource pools can be added
to the cloud at a later time, so this unpredictability should
not be a problem. In some cases, the demand on certain
instance types or flavors may not justify an individual
hardware design. In either of these cases, start by providing
hardware designs which will be capable of servicing the most
common instance requests first, looking to add additional
hardware designs to the overall architecture in the form of
new hardware node designs and resource pools as they become
justified at a later time.</para></section>
cloud. Additional compute resource pools can be added to the cloud
later, reducing the stress of unpredictability. In some cases, the demand on certain
instance types or flavors may not justify individual
hardware design. In either of these cases, initiate the design by
allocating hardware designs that are capable of servicing the most
common instances requests. If you are looking to add additional
hardware designs to the overall architecture, this can be done at
a later time.</para>
</section>
<section xml:id="designing-network-resources-tech-considerations">
<title>Designing network resources</title>
<para>An OpenStack cloud traditionally has multiple network
<title>Designing network resources</title>
<para>OpenStack clouds traditionally have multiple network
segments, each of which provides access to resources within
the cloud to both operators and tenants. In addition, the
network services themselves also require network communication
paths which should also be separated from the other networks.
When designing network services for a general purpose cloud,
it is recommended to plan for either a physical or logical
separation of network segments which will be used by operators
and tenants. It is further suggested to create an additional
network segment for access to internal services such as the
message bus and database used by the various cloud services.
Segregating these services onto separate networks helps to
protect sensitive data and also protects against unauthorized
access to services.</para>
<para>Based on the requirements of instances being serviced in the
cloud, the next design choice, which will affect your design is
the choice of network service which will be used to service
instances in the cloud. The choice between legacy networking (nova-network), as a
the cloud to both operators and tenants. The network services
themselves also require network communication paths which should
be separated from the other networks. When designing network services
for a general purpose cloud, we recommend planning for a physical or
logical separation of network segments that will be used by operators
and tenants. We further suggest the creation of an additional network
segment for access to internal services such as the message bus and
databse used by the various cloud services.
Segregating these services onto separate networks helps to protect
sensitive data and protects against unauthorized access to services.</para>
<para>Based on the requirements of instances being serviced in the cloud,
the choice of network service will be the next decision that affects
your design architecture.</para>
<para>The choice between legacy networking (nova-network), as a
part of OpenStack Compute, and OpenStack Networking
(neutron), has tremendous implications and will have
a huge impact on the architecture and design of the cloud
(neutron), has a huge impact on the architecture and design of the cloud
network infrastructure.</para>
<para>
The legacy networking (nova-network) service is primarily a
layer-2 networking service that functions in two modes. In
legacy networking, the two modes differ in their use of VLANs.
When using legacy networking in a flat network mode, all network
hardware nodes and devices throughout the cloud are connected to
a single layer-2 network segment that provides access to
application data.</para>
<para>When the network devices in the cloud support segmentation
using VLANs, legacy networking can operate in the second mode. In
this design model, each tenant within the cloud is assigned a
network subnet which is mapped to a VLAN on the physical
network. It is especially important to remember the maximum
number of 4096 VLANs which can be used within a spanning tree
domain. These limitations place hard limits on the amount of
growth possible within the data center. When designing a
general purpose cloud intended to support multiple tenants, it
is especially recommended to use legacy networking with VLANs, and
not in flat network mode.</para>
<variablelist>
<varlistentry>
<term>Legacy networking (nova-network)</term>
<listitem>
<para>The legacy networking (nova-network) service is primarily a
layer-2 networking service that functions in two modes. In
legacy networking, the two modes differ in their use of VLANs.
When using legacy networking in a flat network mode, all network
hardware nodes and devices throughout the cloud are connected to
a single layer-2 network segment that provides access to
application data.</para>
<para>When the network devices in the cloud support segmentation
using VLANs, legacy networking can operate in the second mode. In
this design model, each tenant within the cloud is assigned a
network subnet which is mapped to a VLAN on the physical
network. It is especially important to remember the maximum
number of 4096 VLANs which can be used within a spanning tree
domain. These limitations place hard limits on the amount of
growth possible within the data center. When designing a
general purpose cloud intended to support multiple tenants, we
recommend the use of legacy networking with VLANs, and
not in flat network mode.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Another consideration regarding network is the fact that
legacy networking is entirely managed by the cloud operator;
tenants do not have control over network resources. If tenants
@ -161,18 +203,25 @@
such as network segments and subnets, it will be necessary to
install the OpenStack Networking service to provide network
access to instances.</para>
<para>OpenStack Networking is a first class networking
service that gives full control over creation of virtual
network resources to tenants. This is often accomplished in
the form of tunneling protocols which will establish
encapsulated communication paths over existing network
infrastructure in order to segment tenant traffic. These
methods vary depending on the specific implementation, but
some of the more common methods include tunneling over GRE,
encapsulating with VXLAN, and VLAN tags.</para>
<variablelist>
<varlistentry>
<term>OpenStack Networking (neutron)</term>
<listitem>
<para>OpenStack Networking (neutron) is a first class networking
service that gives full control over creation of virtual
network resources to tenants. This is often accomplished in
the form of tunneling protocols which will establish
encapsulated communication paths over existing network
infrastructure in order to segment tenant traffic. These
methods vary depending on the specific implementation, but
some of the more common methods include tunneling over GRE,
encapsulating with VXLAN, and VLAN tags.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Initially, it is suggested to design at least three network
segments, the first of which will be used for access to the
cloud's REST APIs by tenants and operators. This is generally
cloud's REST APIs by tenants and operators. This is
referred to as a public network. In most cases, the controller
nodes and swift proxies within the cloud will be the only
devices necessary to connect to this network segment. In some
@ -197,15 +246,19 @@
resource nodes will need to communicate on this network
segment, as will any network gateway services which allow
application data to access the physical network outside of the
cloud.</para></section>
cloud.</para>
</section>
<section xml:id="designing-storage-resources-tech-considerations">
<title>Designing storage resources</title>
<para>OpenStack has two independent storage services to consider,
<para>OpenStack has two independent storage services to consider,
each with its own specific design requirements and goals. In
addition to services which provide storage as their primary
function, there are additional design considerations with
regard to compute and controller nodes which will affect the
overall cloud architecture.</para></section>
overall cloud architecture.</para> <!--Could there be room for more tech content here? A.S-->
</section>
<section xml:id="designing-openstack-object-storage-tech-considerations">
<title>Designing OpenStack Object Storage</title>
<para>When designing hardware resources for OpenStack Object
@ -217,30 +270,28 @@
attached storage or an external chassis that holds a larger
number of drives, the main goal is to maximize the storage
available in each node.</para>
<para>It is not recommended to invest in enterprise class drives
<para>We do not recommended investing in enterprise class drives
for an OpenStack Object Storage cluster. The consistency and
partition tolerance characteristics of OpenStack Object
Storage will ensure that data stays up to date and survives
hardware faults without the use of any specialized data
replication devices.</para>
<para>A great benefit of OpenStack Object Storage is the ability
to mix and match drives by utilizing weighting within the
swift ring. When designing your swift storage cluster, it is
recommended to make use of the most cost effective storage
<para>One of the benefits of OpenStack Object Storage is the ability
to mix and match drives by making use of weighting within the
swift ring. When designing your swift storage cluster, we
recommend making use of the most cost effective storage
solution available at the time. Many server chassis on the
market can hold 60 or more drives in 4U of rack space,
therefore it is recommended to maximize the amount of storage
per rack unit at the best cost per terabyte. Furthermore, the
use of RAID controllers is not recommended in an object
storage node.</para>
<para>In order to achieve this durability and availability of data
stored as objects, it is important to design object storage
resource pools in a way that provides the suggested
availability that the service can provide. Beyond designing at
the hardware node level, it is important to consider
rack-level and zone-level designs to accommodate the number of
replicas configured to be stored in the Object Storage service
(the default number of replicas is three). Each replica of
therefore we recommend maximizing the amount of storage
per rack unit at the best cost per terabyte. Furthermore, we
do not recommend the use of RAID controllers in an object storage
node.</para>
<para>To achieve durability and availability of data stored as objects
it is important to design object storage resource pools to ensure they can
provide the suggested availability. Considering rack-level and zone-level
designs to accommodate the number of replicas configured to be stored in the
Object Storage service (the defult number of replicas is three) is important
when designing beyond the hardware node level. Each replica of
data should exist in its own availability zone with its own
power, cooling, and network resources available to service
that specific zone.</para>
@ -248,79 +299,116 @@
of requests does not hinder the performance of the cluster.
The object storage service is a chatty protocol, therefore
making use of multiple processors that have higher core counts
will ensure the IO requests do not inundate the server.</para></section>
will ensure the IO requests do not inundate the server.</para>
</section>
<section xml:id="designing-openstack-block-storage">
<title>Designing OpenStack Block Storage</title>
<para>When designing OpenStack Block Storage resource nodes, it is
helpful to understand the workloads and requirements that will
drive the use of block storage in the cloud. In a general
purpose cloud these use patterns are often unknown. It is
recommended to design block storage pools so that tenants can
choose the appropriate storage solution for their
applications. By creating multiple storage pools of different
drive the use of block storage in the cloud. We recommend designing
block storage pools so that tenants can choose appropriate storage
solutions for their applications. By creating multiple storage pools of different
types, in conjunction with configuring an advanced storage
scheduler for the block storage service, it is possible to
provide tenants with a large catalog of storage services with
a variety of performance levels and redundancy options.</para>
<para>In addition to directly attached storage populated in
servers, block storage can also take advantage of a number of
enterprise storage solutions. These are addressed via a plug-in
driver developed by the hardware vendor. A large number of
<para>Block storage also takes advantage of a number of enterprise storage
solutions. These are addressed via a plug-in driver developed by the
hardware vendor. A large number of
enterprise storage plug-in drivers ship out-of-the-box with
OpenStack Block Storage (and many more available via third
party channels). While a general purpose cloud would likely
use directly attached storage in the majority of block storage
nodes, it may also be necessary to provide additional levels
of service to tenants which can only be provided by enterprise
class storage solutions.</para>
<para>The determination to use a RAID controller card in block
storage nodes is impacted primarily by the redundancy and
availability requirements of the application. Applications
which have a higher demand on input-output per second (IOPS)
will influence both the choice to use a RAID controller and
the level of RAID configured on the volume. Where performance
is a consideration, it is suggested to make use of higher
performing RAID volumes. In contrast, where redundancy of
block storage volumes is more important it is recommended to
make use of a redundant RAID configuration such as RAID 5 or
party channels). General purpose clouds are more likely to use
directly attached storage in the majority of block storage nodes,
deeming it necessary to provide additional levels of service to tenants
which can only be provided by enterprise class storage solutions.</para>
<para>Redundancy and availability requirements impact the decision to use
a RAID controller card in block storage nodes. The input-output per second (IOPS)
demand of your application will influence whether or not you should use a RAID
controller, and which level of RAID is required.
Making use of higher performing RAID volumes is suggested when
considering performance. However, where redundancy of
block storage volumes is more important we recommend
making use of a redundant RAID configuration such as RAID 5 or
RAID 6. Some specialized features, such as automated
replication of block storage volumes, may require the use of
third-party plug-ins and enterprise block storage solutions in
order to provide the high demand on storage. Furthermore,
where extreme performance is a requirement it may also be
necessary to make use of high speed SSD disk drives' high
performing flash storage solutions.</para></section>
performing flash storage solutions.</para>
</section>
<section xml:id="software-selection-tech-considerations">
<title>Software selection</title>
<para>The software selection process can play a large role in the
architecture of a general purpose cloud. Choice of operating
system, selection of OpenStack software components, choice of
hypervisor and selection of supplemental software will have a
large impact on the design of the cloud.</para>
<para>The software selection process plays a large role in the
architecture of a general purpose cloud. The following have
a large impact on the design of the cloud:</para>
<itemizedlist>
<listitem>
<para>
Choice of operating system
</para>
</listitem>
<listitem>
<para>
Selection of OpenStack software components
</para>
</listitem>
<listitem>
<para>
Choice of hypervisor
</para>
</listitem>
<listitem>
<para>
Selection of supplemental software
</para>
</listitem>
</itemizedlist>
<para>Operating system (OS) selection plays a large role in the
design and architecture of a cloud. There are a number of OSes
which have native support for OpenStack including Ubuntu, Red
Hat Enterprise Linux (RHEL), CentOS, and SUSE Linux Enterprise
Server (SLES). "Native support" in this context means that the
distribution provides distribution-native packages by which to
install OpenStack in their repositories. Note that "native
support" is not a constraint on the choice of OS; users are
which have native support for OpenStack including:</para>
<itemizedlist>
<listitem>
<para>
Ubuntu
</para>
</listitem>
<listitem>
<para>
Red Hat Enterprise Linux (RHEL)
</para>
</listitem>
<listitem>
<para>
CentOS
</para>
</listitem>
<listitem>
<para>
SUSE Linux Enterprise Server (SLES)
</para>
</listitem>
</itemizedlist>
<note>
<para>Native support is not a constraint on the choice of OS; users are
free to choose just about any Linux distribution (or even
Microsoft Windows) and install OpenStack directly from source
(or compile their own packages). However, the reality is that
many organizations will prefer to install OpenStack from
distribution-supplied packages or repositories (although using
the distribution vendor's OpenStack packages might be a
requirement for support).</para>
(or compile their own packages). However, many organizations will
prefer to install OpenStack from distribution-supplied packages or
repositories (although using the distribution vendor's OpenStack
packages might be a requirement for support).
</para>
</note>
<para>OS selection also directly influences hypervisor selection.
A cloud architect who selects Ubuntu, RHEL, or SLES has some
flexibility in hypervisor; KVM, Xen, and LXC are supported
virtualization methods available under OpenStack Compute
(nova) on these Linux distributions. A cloud architect who
selects Hyper-V, on the other hand, is limited to Windows
Server. Similarly, a cloud architect who selects XenServer is
limited to the CentOS-based dom0 operating system provided
with XenServer.</para>
(nova) on these Linux distributions. However, a cloud architect
who selects Hyper-V is limited to Windows Servers. Similarly, a
cloud architect who selects XenServer is limited to the CentOS-based
dom0 operating system provided with XenServer.</para>
<para>The primary factors that play into OS-hypervisor selection
include:</para>
<variablelist>
@ -350,6 +438,7 @@
</varlistentry>
</variablelist>
</section>
<section xml:id="hypervisor-tech-considerations">
<title>Hypervisor</title>
<para>OpenStack supports a wide variety of hypervisors, one or
@ -380,13 +469,13 @@
</itemizedlist>
<para>A complete list of supported hypervisors and their
capabilities can be found at
<link xlink:href="https://wiki.openstack.org/wiki/HypervisorSupportMatrix">https://wiki.openstack.org/wiki/HypervisorSupportMatrix</link>.
<link xlink:href="https://wiki.openstack.org/wiki/HypervisorSupportMatrix">OpenStack Hypervisor Support Matrix</link>.
</para>
<para>General purpose clouds should make use of hypervisors that
<para>We recommend general purpose clouds use hypervisors that
support the most general purpose use cases, such as KVM and
Xen. More specific hypervisors should then be chosen to
account for specific functionality or a supported feature
requirement. In some cases, there may also be a mandated
Xen. More specific hypervisors should be chosen to account
for specific functionality or a supported feature requirement.
In some cases, there may also be a mandated
requirement to run software on a certified hypervisor
including solutions from VMware, Microsoft, and Citrix.</para>
<para>The features offered through the OpenStack cloud platform
@ -394,7 +483,7 @@
a general purpose cloud that predominantly supports a
Microsoft-based migration, or is managed by staff that has a
particular skill for managing certain hypervisors and
operating systems, Hyper-V might be the best available choice.
operating systems, Hyper-V would be the best available choice.
While the decision to use Hyper-V does not limit the ability
to run alternative operating systems, be mindful of those that
are deemed supported. Each different hypervisor also has their
@ -409,7 +498,9 @@
workloads to utilize software and hardware specific to their
particular requirements. This functionality can be exposed
explicitly to the end user, or accessed through defined
metadata within a particular flavor of an instance.</para></section>
metadata within a particular flavor of an instance.</para>
</section>
<section xml:id="openstack-components-tech-considerations">
<title>OpenStack components</title>
<para>A general purpose OpenStack cloud design should incorporate
@ -445,11 +536,15 @@
<para>A general purpose cloud may also include OpenStack
<glossterm>Object Storage</glossterm> (<glossterm>swift</glossterm>).
OpenStack <glossterm>Block Storage</glossterm>
(<glossterm>cinder</glossterm>) may be
selected to provide persistent storage to applications and
instances although, depending on the use case, this could be
(<glossterm>cinder</glossterm>). These may be
selected to provide storage to applications and
instances.</para>
<note>
<para>However, depending on the use case, these could be
optional.</para>
</note>
</section>
<section xml:id="supplemental-software-tech-considerations">
<title>Supplemental software</title>
<para>A general purpose OpenStack deployment consists of more than
@ -471,7 +566,7 @@
balancers to provide highly available API access and SSL
termination, software solutions, for example HAProxy, can also
be considered. It is vital to ensure that such software
implementations are also made highly available. This high
implementations are also made highly available. High
availability can be achieved by using software such as
Keepalived or Pacemaker with Corosync. Pacemaker and Corosync
can provide active-active or active-passive highly available
@ -481,39 +576,43 @@
infrastructure where one of those nodes may be running certain
services in standby mode.</para>
<para>Memcached is a distributed memory object caching system, and
Redis is a key-value store. Both are usually deployed on
Redis is a key-value store. Both are deployed on
general purpose clouds to assist in alleviating load to the
Identity service. The memcached service caches tokens, and due
to its distributed nature it can help alleviate some
bottlenecks to the underlying authentication system. Using
memcached or Redis does not affect the overall design of your
architecture as they tend to be deployed onto the
infrastructure nodes providing the OpenStack services.</para></section>
infrastructure nodes providing the OpenStack services.</para>
</section>
<section xml:id="performance-tech-considerations">
<title>Performance</title>
<para>Performance of an OpenStack deployment is dependent on a
number of factors related to the infrastructure and controller
services. The user requirements can be split into general
network performance, performance of compute resources, and
performance of storage systems.</para></section>
performance of storage systems.</para>
</section>
<section xml:id="controller-infrastructure-tech-considerations">
<title>Controller infrastructure</title>
<para>The Controller infrastructure nodes provide management
services to the end-user as well as providing services
internally for the operating of the cloud. The Controllers
typically run message queuing services that carry system
run message queuing services that carry system
messages between each service. Performance issues related to
the message bus would lead to delays in sending that message
to where it needs to go. The result of this condition would be
delays in operation functions such as spinning up and deleting
instances, provisioning new storage volumes and managing
network resources. Such delays could adversely affect an
application's ability to react to certain conditions,
application’s ability to react to certain conditions,
especially when using auto-scaling features. It is important
to properly design the hardware used to run the controller
infrastructure as outlined above in the Hardware Selection
section.</para>
<para>Performance of the controller services is not just limited
<para>Performance of the controller services is not limited
to processing power, but restrictions may emerge in serving
concurrent users. Ensure that the APIs and Horizon services
are load tested to ensure that you are able to serve your
@ -522,11 +621,13 @@
authentication and authorization for all services, both
internally to OpenStack itself and to end-users. This service
can lead to a degradation of overall performance if this is
not sized appropriately.</para></section>
not sized appropriately.</para>
</section>
<section xml:id="network-performance-tech-considerations">
<title>Network performance</title>
<para>In a general purpose OpenStack cloud, the requirements of
the network help determine its performance capabilities. For
the network help determine performance capabilities. For
example, small deployments may employ 1 Gigabit Ethernet (GbE)
networking, whereas larger installations serving multiple
departments or many users would be better architected with
@ -535,7 +636,8 @@
environments that run a mix of networking capabilities. By
utilizing the different interface speeds, the users of the
OpenStack environment can choose networks that are fit for
their purpose. For example, web application instances may run
their purpose.</para>
<para>For example, web application instances may run
on a public network presented through OpenStack Networking
that has 1 GbE capability, whereas the back-end database uses
an OpenStack Networking network that has 10&nbsp;GbE capability to
@ -547,7 +649,9 @@
perform SSL termination if that is a requirement of your
environment. When implementing SSL offloading, it is important
to understand the SSL offloading capabilities of the devices
selected.</para></section>
selected.</para>
</section>
<section xml:id="compute-host-tech-considerations">
<title>Compute host</title>
<para>The choice of hardware specifications used in compute nodes
@ -562,12 +666,14 @@
Compute environment to avoid this scenario. For running
general purpose OpenStack environments it is possible to keep
to the defaults, but make sure to monitor your environment as
usage increases.</para></section>
usage increases.</para>
</section>
<section xml:id="storage-performance-tech-considerations">
<title>Storage performance</title>
<para>When considering the performance of OpenStack Block Storage,
hardware and architecture choices are important. Block Storage
can use enterprise back-end systems such as NetApp or EMC, use
<para>When considering performance of OpenStack Block Storage,
hardware and architecture choice is important. Block Storage
can use enterprise back-end systems such as NetApp or EMC,
scale out storage such as GlusterFS and Ceph, or simply use
the capabilities of directly attached storage in the nodes
themselves. Block Storage may be deployed so that traffic
@ -577,13 +683,15 @@
dedicated interfaces on the Controller and Compute
hosts.</para>
<para>When considering performance of OpenStack Object Storage, a
number of design choices will affect performance. A user's
number of design choices will affect performance. A user’s
access to the Object Storage is through the proxy services,
which typically sit behind hardware load balancers. By the
which sit behind hardware load balancers. By the
very nature of a highly resilient storage system, replication
of the data would affect performance of the overall system. In
this case, 10 GbE (or better) networking is recommended
throughout the storage network architecture.</para></section>
throughout the storage network architecture.</para>
</section>
<section xml:id="availability-tech-considerations">
<title>Availability</title>
<para>In OpenStack, the infrastructure is integral to providing
@ -611,16 +719,16 @@
your systems, will help determine scale out decisions.</para>
<para>Care must be taken when deciding network functionality.
Currently, OpenStack supports both the legacy networking (nova-network)
system and the newer, extensible OpenStack Networking. Both
system and the newer, extensible OpenStack Networking (neutron). Both
have their pros and cons when it comes to providing highly
available access. Legacy networking, which provides networking
access maintained in the OpenStack Compute code, provides a
feature that removes a single point of failure when it comes
to routing, and this feature is currently missing in OpenStack
Networking. The effect of legacy networking's multi-host
Networking. The effect of legacy networking’s multi-host
functionality restricts failure domains to the host running
that instance.</para>
<para>On the other hand, when using OpenStack Networking, the
<para>When using OpenStack Networking, the
OpenStack controller servers or separate Networking
hosts handle routing. For a deployment that requires features
available in only Networking, it is possible to
@ -632,9 +740,8 @@
Networking, and instead rely on hardware routing capabilities.
In this case, the switching infrastructure must support L3
routing.</para>
<para>
OpenStack Networking (neutron) and legacy networking
(nova-network) both have their advantages and
<para>OpenStack Networking and legacy networking
both have their advantages and
disadvantages. They are both valid and supported options that
fit different network deployment models described in the
<citetitle><link
@ -661,12 +768,12 @@
may include utilizing shared file systems on enterprise
storage or OpenStack Block storage to provide a level of
guarantee to match service features.</para>
<para>
For more information on high availability in OpenStack, see the <link
<para>For more information on high availability in OpenStack, see the <link
xlink:href="http://docs.openstack.org/high-availability-guide"><citetitle>OpenStack
High Availability Guide</citetitle></link>.
</para>
</section>
</section>
<section xml:id="security-tech-considerations">
<title>Security</title>
<para>A security domain comprises users, applications, servers or
@ -751,7 +858,7 @@
the API services behind hardware that performs SSL termination
is strongly recommended.</para>
<para>
For more information on OpenStack Security, see the <link
For more information OpenStack Security, see the <link
xlink:href="http://docs.openstack.org/security-guide/"><citetitle>OpenStack
Security Guide</citetitle></link>
</para>