Understanding and Planning

This chapter describes what WPAR technology is and how it can be implemented
to work in your IT environment. The chapter is designed to provide system
architects and system administrators the level of knowledge required to plan the
deployment of WPARs in their IT infrastructure.
This chapter will discusses high level positing of WPARs and how it complements
and works with the powerful suite of products for virtualization, high availability
and server consolidation in System p, while helping to provide a higher level of
service to the applications and ultimately the end user of these ever growing and
changing environments. This chapter includes the following sections:
2.1, “High-level planning information” on page 20
2.2, “General considerations” on page 21
2.3, “Global environment considerations” on page 26
2.4, “Application WPARs” on page 27
2.5, “System WPARs” on page 28
2.6, “WPAR mobility.” on page 31
2.7, “WPAR and LPAR comparison” on page 36
2
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20 Workload Partitions in IBM AIX Version 6.1
2.1 High-level planning information
The WPAR technology is purely software based. It can therefore be deployed on
any hardware platform that supports AIX 6:
IBM eServer™ pSeries with POWER4 processors
IBM System p
IBM BladeCenter® JS21 with PPC 970 processors
The WPAR offering consists of two parts:
1. IBM AIX Version 6.1 contains the base support for WPAR technology. This
includes creation and management of both application and system workload
partitions within the LPAR where AIX 6 is installed. AIX provide WPAR
support and management through the AIX command line interface and SMIT
menus.
2. IBM Workload Partitions Manager for AIX is a optional separately installable
licensed program product that supports more advanced features:
– Graphical User Interface including wizards for most management activity.
– Management of multiple WPARs on multiple servers from a single point of
control
– Enablement for WPAR mobility
– Automated and policy-based WPAR mobility.
The decision to use WPAR technology depends on the potential benefits that this
technology can yield to a specific user environment. These benefits have been
described in Section 1.5, “When to use workload partitions” on page 13.
Once the decision to use WPAR has been taken, the planning activity consists
then in deciding:
which is the best suited workload partitions type: application to system
WPARS?
if application mobility will be required?
The answer to these questions have technical consequences that are described
in the following sections.
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2.2 General considerations
The WPAR provides isolation of software services, applications and
administration utilizing flexible software-defined boundaries within a single
instance of the AIX 6.1 operating system (Global). When building a WPAR from
the command line you can configure and start it within a few minutes.
This technology presents system administrators with new planning challenges
concerning network, filesystems and OS versions. Networks aliases, shared or
NFS filesystems, and kernel unicity require a different approach to planning of
applications deployment.
2.2.1 Networking
When planning for networks, one must understand how to get the most of this
technology. Using alias decreases the number of adapters needed for
communications but implies a careful planning of bandwidth utilization, since
several WPARs may share the same adapter.
NFS is a prerequisite to the WPAR mobility functionality. Three components are
involved in NFS communications for WPAR mobility:
the name and IP address of the global environment,
the name and IP address of the WPAR
and the name and IP address of the NFS server.
Since they all play a role in this communication they all must know each other.
Preferably put them all in the same subnet. For more detailed explanations check
Chapter 6, “IBM WPAR Manager for AIX” on page 125.
2.2.2 Deployment of the WPAR manager
The WPAR Manager provides a central systems management solution by
providing a set of web-based systems management tools and tasks simplifying
the management of a customer server and WPAR infrastructure.
The WPAR Manager offers infrastructure resource optimization, service
performance optimization and service availability optimization tools. Specific
features of the Workload Partition Manager include, centralized, single point of
administrative control for managing both system and application WPARs,
browser-based GUI for dynamic resource management, system and application
level workload management through WPARs, provide Role-based views and
tasks, dynamic allocation/reallocation and configuration of virtual servers,
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22 Workload Partitions in IBM AIX Version 6.1
storage, network, and non-interruptive maintenance zero downtime for server
fixes and upgrades through virtual server relocation
Using the WPAR Manager involves three roles:
– A WPAR Management Server which is a java application running in an AIX
server. This can be a stand alone server or a an LPAR in a shared physical
server. (dedicated or micropartition).
– The WPAR Management clients which are installed in each LPAR where
WPAR are planned to be deployed and communicates with the WPAR
Management Server
– The WPAR Manager User Interface is a light-weight browser-supported
interface to the WPAR Management Server. The interface can be provided
by any web browser with an IP connection to the WPAR Management
Server. The UI allows for display of information that has been collected
through the agents, and also provides management capability such as
creation, deletion, relocation of WPARs.
Figure 2-1 shows where the components of the WPAR manager execute.
Chapter 2. Understanding and Planning for WPARs 23
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Figure 2-1 Workload Partitions (WPARs) running in POWER4, 5, 5+, or 6 nodes
When planning the deployment of WPAR Manager components on different
LPARS and workstation, the network firewalls must be configured to allow traffic
to the specific ports listed on Figure 2-2.
Ports 14080 and 14443 are used for communication between the system
administrator workstation and the WPAR Manager.
Note: This figure contains the default value of ports used by the WPAR
Manager. The system administrator can modify these values when configuring
the WPAR Manager.
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24 Workload Partitions in IBM AIX Version 6.1
Ports 9510, 9511, 9512 and 9513 are used for communications between the
agents and managers.
Figure 2-2 TCPIP ports to configure on firewall to use the WPAR manager
2.2.3 Software prerequisites
Having a single instance of AIX simplifies the installation and general
administration of the WPARs. Software is installed once and used many times in
many WPARs. Although totally isolated from each other, these WPARs use the
same AIX kernel instance. This means that all WPARs use the exact same level
of AIX. When planning for WPARs, one must make sure that all applications
software support the level of AIX of the global environment. More important, plan
for the future. Updating or upgrading AIX in the global environment means
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updating or upgrading AIX in all hosted WPARs environment. If you have an
application that needs a specific version of AIX and cannot be updated, move it
to a different LPAR so that it does not prevent the other WPARs from updating.
2.2.4 File system considerations
System WPARs created with the default options have shared read-only /usr and
/opt filesystems. This speeds up the creation, installation and updating of WPARs
and also prevents the accidental removal of system software shared with other
WPARs. Having the read-only shared /usr and /opt filesystem may not suit every
applications: some applications are designed to write in the /usr or /opt
filesystems. One solution is to defined the needed application’s writable directory
as a different filesystem and link it to the mountpoint the application
needs.Chapter 5.3.3, “Shared /usr with writable filesystem” on page 98 explains
how a WPAR can have a writable directory under a read-only /usr or /opt.
Another solution is for the application to not use the global environment shared
/usr or /opt filesystems. This solution requires extra disk space because it
duplicates the global environment’s /usr or /opt to WPAR’s private and fully
writable filesystems.
Consolidating many applications within one global environment changes the way
the system administrator manages filesystems. Instead of managing multiple
LPARs, each with a few filesystems, he now manages only one LPAR with many
filesystems. In both case, the overall number of filesystems remains in the same
order of magnitude (although using WPARs slightly reduces this number), but
they are controlled within a single system. By default, a system WPAR has 4
dedicated filesystems, and 2 shared read-only and the /proc filesystem. For
example, deploying 200 system WPARs in one global environment will result by
default in a global environment with 800 separate filesystems, and 1200 mount
points in the /proc pseudo-filesystems. The WPAR technology provides an option
to reduce this number of filesystems. Instead of using the default filesystem
creation option, the system administrator can choose to create one single
filesystem per WPAR, as described in Chapter 5.1.4, “Creating WPARs:
advanced options” on page 75. Basically, this solution creates only one real
filesystem (the root “/” filesystem) for the WPAR, and subtrees /var, /tmp, /home
are just created as subdirectories of the “/” filesystem, instead of real filesystems
as they usually are in AIX instances and default system WPAR
Filesystems of each system WPAR are created in the global environment
directory tree and are mounted under the WPAR base directory. One base
directory is defined per WPAR. The default path of the base directory is
/wpars/. When planning to deploy several system partitions, the
system administrator may want to organize base directory in a different directory
tree organization.
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26 Workload Partitions in IBM AIX Version 6.1
Section 2.4 to 2.6 explains in more details filesystems considerations for
respectively application WPARs, system WPARs and when mobility is used.

When to use workload partitions

Workload Partitions offer new possibilities for managing AIX environments. They
complement other virtualization solutions available for System p6 platforms. The
following scenarios are examples of when you could benefit from using WPARs.
1.5.1 Improvement of Service Level Agreements
Hardware components of an IT infrastructure may need to undergo maintenance
operations requiring the component to be powered off. If an application is not
part of a cluster of servers providing continuous availability, either for technical,
organizational or cost reasons, then WPARs can help to reduce the application
downtime. Using the live partition mobility feature, the applications that are
executing on a physical server can be temporarily moved to another server,
without an application blackout period during the period of time required to
perform the server physical maintenance operations.
Long running jobs can take advantage of the checkpoint/restart feature of
WPARs. It can be used to protect them against a failure which would require
restarting all computation from scratch. The checkpoint feature can be used to
regularly capture a snapshot of the application runtime environment, without
having to instrument the code. In the case where the job would need to be
stopped before reaching completion of the computation, the job can be resumed
in the state it was when the last checkpoint was saved.
The checkpoint/restart feature can also be used to execute long lasting batch
jobs on a system with limited resources. This job can be run at night time, be
paused during the daytime, when the computer resources have to be dedicated
to other applications, such as transaction handling or web serving, and then
resumed at the beginning of the next night.
The workload partition technology can also help in an environment where an
application needs to be started often, on-demand, and quickly. This may apply,
for example, in test environments where resources are too scarce to keep
multiple application executing concurrently when not in use. Using WPARs, many
applications can be defined on a server, but not activated. Activation of the
workload partitions executing each of these application can be performed only
when needed for a test.
1.5.2 Protection of legacy hardware investment
Although customers using POWER4 IBM Eserver pSeries® servers cannot
take advantage of physical or hypervisor based virtualization technology, the
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14 Workload Partitions in IBM AIX Version 6.1
WPAR technology relies only on IBM AIX Version 6.1, with no dependency on the
underlying hardware. It can be used on POWER4, POWER5 and POWER6
based servers.
Customers having many applications, each running an a dedicated POWER
based server or dedicated partition, and requiring only a fraction of the available
processing power can, thanks to the WPAR technology, consolidate these
application within one LPAR. Each application can be executed within one
WPAR, providing a dedicated environment isolated from the other applications
environments, while all WPARs share the physical resource of one LPAR.
1.5.3 Optimization of resource usage
The IBM System p family offers many ways to optimize resource utilization
through virtualization technologies, such as LPARs, DLPARs, and
micropartitions. The WPAR technology complements the existing solution
offerings thanks to its unique characteristics.
The WPAR technology gives you additional flexibility in system capacity planning
as part of a strategy for maximizing system utilization and provisioning efficiency.
Due to the static allocation of partitions in physical servers, in a typical IT
environment, each server is sized with spare capacity to allow for resource
consumption increase of all applications executing within this server. Thanks to
the mobility feature of WPARs, the server sizing and planning can be based on
the overall resources of a group of servers, rather than being performed server
per server. It is possible to allocate applications to one server up to 100% of its
resources. When an application grows and requires resources that can no longer
be provided by the server, the application can be moved to a different server with
spare capacity.
The same mobility feature, combined with the policy based relocation functions
of the WPAR Manager allows to size a set of servers to handle the peak load,
based on the overall resource capacity of the set of server, and not for each
server. In a classical environment, each server must be able to support the peak
load of all partitions hosted within this server. Thanks to the WPAR mobility, it is
possible to take advantage of free resources in one physical server to offload
another physical server hosting applications that require more resources than
locally available.
AIX 6 provides very fine grained control of CPU and memory resource allocation
to workload partitions (down to 0.01% increments). This technology is therefore
suitable for server consolidation of very small workloads. This could be
particularly interesting for the replacement of old servers, for which even 10% of
one POWER5 or POWER6 processor, (the smallest micropartition) exceeds the
application needs.
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The theoretical upper limit on the number of workload partitions that can be
executed within one LPAR is 8192. In actual practice, your application
environment will probably require far less than 8192 WPARs running within a
single LPAR. And in practice we would expect you would encounter other AIX
system limitations preventing you from actually approaching this theoretical limit.
1.5.4 Fine grain control of resource allocation
When multiple applications are executing within the same AIX instance, the
system administrator may want to control how much cpu and memory resources
are used by each application. One way to perform this control is to set up the
Workload Manager (WLM) functions which is part of standard AIX features.
The WPAR technology provides a new way to perform this resource control. The
WPAR resource control is reusing the WLM technology, but encapsulates it in a
way that WLM is not visible to the system administrator. There is no need for the
system administrator to know about WLM. The resource control is available
through options of the WPAR command line and SMIT interfaces.
The WPAR resource control feature allows the system administrator to arbitrate
between applications competing for CPU and memory resources. This
guarantees that each application receives a share of the cpu and memory
resource available from the global environment. These resources are separate
from the requirements of the other applications executing in WPARs within the
same operating system instance.
1.5.5 Control of security and privilege command
In large AIX environments, where a partition hosts many applications, it is not
unusual to have multiple people acting as system administrators. However, all of
them may not have the need for root or superuser privileges in all domains of
system administration. They can be specialized for activities such as for example
user administration, network control, storage control, or software maintenance.
The WPAR technology supports this specialization of roles, and can help restrict
the privileges given to one person to just the scope he needs to control. System
workload partitions have their own user set, independent from the user set
defined at the global environment level. An individual who is using root within a
Note: In practice, the number of WPARs which could be created and made
active in an LPAR depends upon the capacity of the system, the configuration
of the WPARs, and the characteristics of the applications being run in those
WPARs.
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16 Workload Partitions in IBM AIX Version 6.1
system workload partition only has superuser privileges for the resources visible
within this WPAR. He cannot control global environment resources, such as
network adapter or physical devices, and he cannot act on resources belonging
to other workload partitions. Many application have the need for the application
administrator to use the root user to control the application, even if this person
does not need to manage the operating system. The WPAR technology allows to
delegate the superuser privileges to one individual, and limit them to an
application environment, without jeopardizing the global environment.
The separation of user sets (or security domains) between different system
workload partitions also enables the system administrators to isolate groups of
users logging on in AIX environments according to their application access
control requirements. Users defined in one system WPAR are unaware of the
applications executing in the global environment or in other WPARs. They can’t
see the list of users or processes outside their WPAR.
IBM AIX Version 6.1 provides improvement over the previous AIX 5L™ Version
5.3 for role based control of user privileges. This feature is known as Role Based
Access Control (RBAC). An exhaustive description of these new features is
available in IBM AIX V6.1 Security Enhancements, SG24-7430.
WPAR integrates the use of RBAC features for controlling privileges. A default
RBAC setting is provided with each WPAR, but the system administrator can also
further customize the RBAC configuration used in a WPAR context.
1.5.6 Simplified handling of software stack
The WPAR technology can help the system administrator simplify the way he
maintains the operating systems and application software stacks.
A traditional approach to application deployment has been for a long time to
dedicate one server to one application. With the advent of virtualization and
partitioning technologies, it has been possible to host multiple applications within
partitions of a physical server. But this solution still implies that the system
administrator needs to maintain one operating system instance for each
application. The WPAR technology allows to share an AIX instance between
multiple applications, while still running each application within its own
environment, providing isolation between application. In this case, the more
applications that are consolidated within one AIX instance, the less the system
administrator has to perform OS fix applications, backups, migration, and other
OS maintenance tasks. However, it must be noted that such a consolidation
requires that all applications can run under the same version and maintenance
level of the OS.
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In addition to sharing the operating system, the system administrator can take
advantage of the WPAR technology to share application code. In a traditional AIX
environment, if several Apache web servers are needed, they would each be
deployed in a dedicated server or LPAR. In a WPAR environment, it is possible to
install Apache in one LPAR, and then execute multiple instances of the Apache
server within this LPAR, by starting multiple WPARs. Each WPAR runs its own
Apache server, with its own data in dedicated disk space, but shares the Apache
code with all other WPARs. Such a configuration optimizes memory utilization by
eliminating duplication of code, and reduces administration maintenance of the
Apache code, which only needs to be updated once for all server instances.
IBM AIX Version 6.1 introduces a new concept in software installation and
management: relocatable software packages. A relocatable application is an
application where the files can be installed relative to a base directory which is
different from the / root directory of the AIX environment. Using this feature, it is
possible to deploy multiple versions of the same application within one AIX
instance. The system administrator can take advantage of relocatable
application, by starting each version of the application in a specific WPARs,
therefore providing multiple servers with different server code version, from one
LPAR.
1.5.7 Simplified handling of application OS environment.
The workload partition configuration can be stored in human-readable
specification files. These specification files can be generated by the operating
system from already existing workload partitions, or can be edited, created or
modified by hand. In an environment where a system administrator has to
manage several application environments, the WPAR technology can help him
quickly clone and define new application environments. These specification files
can be used as input to WPAR creation commands, allowing the system
administrator to automate through scripts and programs the startup and handling
of multiple workload partitions.
1.5.8 Business continuity: disaster/failure recovery:
The WPAR technology can be integrated as one element of a solution to provide
a business continuity plan.
The checkpointing feature of WPAR allows to capture a snapshot of an executing
application without having to instrument the code. The application checkpoint
image is then saved to a file that can later be used to resume execution of an
application. Combined with a backup of the application data, the WPAR
checkpoint feature can provide an alternate disaster or failure recovery solution
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18 Workload Partitions in IBM AIX Version 6.1
for application that do not use other solutions such as HACMP™ or server
clusters.
1.5.9 Supporting “Green” computing strategies
Using WPAR relocation features for live application mobility means you have the
flexibility to consolidate workloads during periods of low usage onto smaller
numbers of operating server platforms. In this strategy you still provide
continuous application availability, but you do so using a smaller number of
powered up servers. As you approach normal high usage periods you could then
power up additional peak demand server resources and relocate cyclic
workloads back to those machines during those peak demand periods. For
example, if your data center peak workload periods are 12 hrs per day, 5 days
per week, then peak load systems would only need to be powered up ~%35 of
the time.

Live application mobility

Both types of workload partitions, the system WPAR and the Application WPAR,
are capable of being configured to support mobility, or relocation.
The ability to move one WPAR from one LPAR to another, possibly from one
physical system to another, can be executed on active partitions. In this case the
application undergoes active relocation (it is hot-migrated), without stopping the
Note: In 2007, IBM’s System p6 and AIX 6 have 2 features that seem similar,
but are different: WPAR mobility & live partition mobility
– WPAR mobility, which is discussed in this book, is a feature of AIX 6 and
WPAR Manager. It is available on POWER4, POWER5, and POWER6
systems.
– Live partition mobility relies on the POWER6 hardware and hypervisor
technology (Advance Power Virtualization). It is available on POWER6
systems only. This feature is also available to AIX 5.3 LPARs.
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12 Workload Partitions in IBM AIX Version 6.1
application. The only visible effect for a user of the application is a slightly longer
response time while the application is migrating.
Workload partition mobility uses checkpoint & restart features to move workload
partitions. The checkpoint saves the current status of the application and then
restarts it on a new system or OS instance at the previously saved state.
Partition mobility is not a replacement for a High Availabilty solution. The premise
is to allow for planned migrations of workloads from one system to another while
the application is not interrupted. This could be the case for hardware
maintenance or a firmware installation on the server. The workload does not
need to be aware of the migration for the most part. But proper planning and
testing are always recommended before moving anything into a production
environment
Figure 1-4 depicts the use of WPAR relocation for workload balancing where two
applications are moved between two server to balance the load of these servers.
This figure also introduce the concept of WPAR manager that will be described in
Chapter 2, “Understanding and Planning for WPARs” on page 19.
Figure 1-4 WPAR migration
Important: Workload partition mobility is a software solution that is dependent
on AIX 6 for execution. When used for the migration of a WPAR from one
LPAR to another or between physical systems, then hardware and software
compatibility is required.