WPAR and LPAR comparison

IBM has taken a leadership role in innovation, over the past fourteen years and
has been number one in the patent technology race. Out of this has come a
plethora of new and innovative products. In 2001 IBM announced the LPAR
feature on IBM eServer pSeries and then in 2004 Advanced Power Virtualization
provided the micropartitioning feature. In 2007, IBM announces WPAR Mobility.
WPARs are not a replacement to LPARs. These two technologies are both key
components of IBM's virtualization strategy. The two technologies are
complementary, and can be used together to extend their individual values.
Providing both LPAR and WPAR technology offers a broad range of virtualization
choices to meet the ever changing needs in the IT world. Table 2-2 compares
and contrasts the benefits of the two technologies.
Table 2-2 Comparing WPAR and LPAR
Workload Partitions Logical Partitions
WPARs share OS images LPARs execute OS images
Finer-grained resource management,
per-workload
Resource management per LPAR
Capacity on demand
Security isolation Stronger security isolation
Easily shared files and applications Supports multiple OSes, Tunable to
applications
Lower administrative costs:
1 OS to manage
Easy create/destroy/configure
Integrated management tools
OS Fault isolation
Chapter 2. Understanding and Planning for WPARs 37
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Figure 2-7 shows how LPAR and WPARs can be combined within the same
physical server, which also hosts the WPAR Manager and NFS server required to
support partition mobility.
Important: When considering the information in Table 2-2 you should keep in
mind the following guidelines:
In general, when compared to WPARs, LPARs will provide a greater
amount of flexibility in supporting your system virtualization strategies.
Once you have designed an optimal LPAR resourcing strategy, then within
that strategy you design your WPAR strategy to further optimize your
overall system virtualization strategy in support of AIX6 applications. See
Figure 2-7 for an example of this strategy, where multiple LPARs are
defined to support different OS and application hosting requirements, while
a subset of those LPARs running AIX6 are setup specifically to provide a
global environment for hosting WPARs.
Because LPAR provisioning is hardware/firmware based you should
consider LPARs as a more secure starting point for meeting system
isolation requirements than WPARs.
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38 Workload Partitions in IBM AIX Version 6.1

WPAR mobility.

Live Application Mobility is the newest virtualization technology from IBM. This is
a software approach that enhances the current line of technology. Live
Application Mobility is a complement to IBM’s line of virtualization package. The
premise is to allow for planed migrations of workloads from one system to
another whilst the application is not interrupted. This could be used for example
to perform a planned firmware installation on the server. Most workload do not
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32 Workload Partitions in IBM AIX Version 6.1
need to be aware of the WPAR relocation. But proper planning and testing are
always recommended before moving anything into a production environment.
WPAR mobility, also referred to as relocation, applies to both type of WPAR:
application and system. The relocation of a WPAR consists in moving its
executable code from one LPAR to another one, while keeping the application
data on the same storage devices. It is therefore mandatory that these storage
devices are accessible from both the source and target LPARs hosting the
WPAR.
In the initial version of AIX 6, this dual access to the storage area is provided
thanks to NFS. As mentioned previously, the hosting global environment hides
the physical and logical device implementations from the hosted WPARs. The
WPAR only deals with data storage at filesystem level. All files that needs to be
written by the application must be hosted on an NFS filesystem. All other files,
including the AIX operating systems files can be stored in filesystems local to the
hosting global environment. Table 2-1 helps planning the creation of the
filesystems for an application that requires WPAR mobility, when hosted in an
application or system workload partition, for an application which only writes in
filesystems dedicated to the application.
Table 2-1 Default filesystem location to enable partition mobility
Figure 2-5 on page 33 shows an example of a complete environment in which to
deploy LPARs and WPARs on two p595 systems.
The first global environment, called saturn, and is hosted in an LPAR of the first
p595. It is a client of the NFS server as well as titian, the system WPAR inside of
it. The second system is also a p595, but could be any of the same class of
systems from the p505 on up. One of its LPARs hosts a global environment
called jupiter, which is also a client of the NFS server.
Filesystem Application WPAR System WPAR
/ Global environment NFS mounted
/tmp Global environment NFS mounted
/home Global environment NFS mounted
/var Global environment NFS mounted
/usr Global environment Global environment
/opt Global environment Global environment
application specific NFS mounted NFS mounted
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There a utility server and for the example it is a p550. On this system there is an
NFS server, a NIM server and a WPAR Manager for AIX to provide the single
management point need for all the WPARs. The NIM server is in the picture to
represent how to load AIX images into the frame which could have a large
number of LPARs. The NFS server is for providing an outside the box filesystem
solution to the WPARs and provide the vehicle to move them on the fly from one
system to another with out disrupting the application.
Figure 2-5 Overview of the topology requirements in a mobile WPAR solution
The NFS server is a standard configuration and is utilizing either NFS protocols
version 3 or version 4. Command line editing or the use of SMIT can be used to
configure the /etc/exports.
Figure 2-6 is a representation of the relationship between the different views of
the same filesystems as seen:
from the NFS server where they are physically located,
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34 Workload Partitions in IBM AIX Version 6.1
from the global environments on which they are NFS-mounted, and
from the system WPAR that uses them.
In the WPAR, the /opt, /proc and /usr are setup as namefs with read-only
permissions (exception: /proc is always read-write) mapping on the global
environment /opt, /proc and /usr. The rest of the filesystems (/, /home, /tmp and
/var) are setup as standard NFS. The /etc/exports file on the NFS server must
have permissions set for both the global environment (jupiter) and system WPAR
(ganymede) for the mobility to work.
Important: The NFS server must provide access to both the global
environment and the WPAR in order for the WPAR to work at all. In a mobility
scenario, access must be provided to the WPAR and all global environments
to which the WPAR may be moved. Furthermore, any time /, /var, /usr, or /opt
are configured as NFS mounts, the NFS server must provide root access (e.g.
via the -r option to mknfsexp) to all of the relevant hostnames.
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Figure 2-6 Filesystems from the NFS for a Mobile System WPAR
Using the df command as in shows that the global environment jupiter has its
own filesystems hosted on locally attached disks as well as NFS filesystems
mounted from the gracyfarms NFS server, for use by the for ganymede system
WPAR.
Example 2-5 NFS server mountpoints for ganymede WPAR
root: jupiter:/wpars/ganymede --> df
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/hd4 131072 66376 50% 1858 6% /
/dev/hd2 3801088 646624 83% 32033 7% /usr
/dev/hd9var 524288 155432 71% 4933 8% /var
/dev/hd3 917504 233904 75% 476 1% /tmp
/dev/hd1 2621440 2145648 19% 263 1% /home
/proc - - - - - /proc
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36 Workload Partitions in IBM AIX Version 6.1
/dev/hd10opt 1572864 254888 84% 7510 4% /opt
gracyfarms:/big/ganymede/root 131072 81528 38% 1631 16% /wpars/ganymede
gracyfarms:/big/ganymede/home 131072 128312 3% 5 1% /wpars/ganymede/home
/opt 1572864 254888 84% 7510 4% /wpars/ganymede/opt
/proc - - - - - /wpars/ganymede/proc
gracyfarms:/big/ganymede/tmp 262144 256832 3% 12 1% /wpars/ganymede/tmp
/usr 3801088 646624 83% 32033 7% /wpars/ganymede/usr
gracyfarms:/big/ganymede/var 262144 229496 13% 1216 5% /wpars/ganymede/var

Application WPARs

There are two different types of workload partitions. The simplest is application
WPAR. It can be viewed as a shell which spawns an application and can be
launched from the global environment. This is a light weight application resource:
It does not provide remote login capabilities for end users. It only contain a small
number of processes, all related to the application, and uses services of the
global environment daemons and processes.
It shares the operating system filesystems with the global environment. It can be
setup to receive its application filesystem resources from disks owned by the
hosting AIX instance, or from a NFS server.
Figure 2-3 on page 28 shows the relationship of an application WPAR
filesystems to the default global environment filesystems. The filesystems that
are visible to processes executing within the application WPAR are the global
environment filesystems shown by the relationships in the figure.
If an application WPAR accesses data on an NFS mounted filesystem, this
filesystem must be mounted in the global environment directory tree. The mount
point is the same, when viewed from within the WPAR than when viewed from
the global environment. The system administrator of the NFS server must
configure the /etc/exports file so that filesystems are exported to both the global
environment IP address and to the application WPAR IP address.
Processes executing with an application WPAR can only see processes that are
executing within the same WPAR. In other words, the use of Inter Process
Communication (IPC) by application software is limited to the set of processes
within the boundary of the WPAR.
Applications WPARs are temporary objects. The life-span of an application
WPAR is the life-span of the application it hosts. An application WPAR is created
at the time the application process is instantiated. The application WPAR is
destroyed when the last process running within the application partition exits. An
application WPAR is candidate for mobility. It can be started in one LPAR, and
relocating to other LPARs during the life of its hosted application process.
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28 Workload Partitions in IBM AIX Version 6.1
Figure 2-3 File system relationships from the global environment to the Application WPAR
2.5 System WPARs
The second type of WPAR is a system WPAR. A system WPAR provides a typical
AIX environment for executing applications, with some restrictions. A system
WPAR has its own runtime resources. It contains an init process that can spawn
daemons. For example, it has its own inetd daemon to provide networking
services, and own System Resource Control (SRC).
Every system WPAR has its own unique set of users, groups and network
interface addresses. The users and groups defined within a system WPAR are
completely independent from the users and groups defined at the global
environment level. In particular, the root user of the WPAR only has superuser
privileges within this WPAR, and has no privilege in the global environment (In
fact, the root and other users defined in within the WPAR cannot even access the
global environment). In the case of a system partition hosting a database server,
the DB administrator can for example be given root privilege within the DB
WPARs, without giving him any global environment privilege.
The environment provided by a system WPAR to its hosted application and
processes is a chroot complete AIX environment, with access to all AIX systems
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files that are available in a native AIX environment. The creation of a system
WPAR includes the creation of a base directory, referred to as the base directory
in the WPAR documentation. This base directory is the root of the chroot system
WPAR environment. By default, the path to this base directory is
/wpars/ in the global environment.
By default, the base directory contains 7 filesystems:
/, /home, /tmp and /var are real filesystems, dedicated to the system partition
use.
/opt and /usr are read-only namefs mounts over the global environment’s /usr
and /opt.
the /proc pseudo-filesystem maps to the global environment /proc
pseudo-filesystem (/proc in a WPAR only makes available process
information for that WPAR).
Figure 2-4 depicts an overview of these filesystems, viewed from the global
environment and from within the system WPAR. In this example, a WPAR called
titian is hosted in an LPAR called saturn. Although the diagram shows the global
environment utilizing VIOs with two vscsi adapter along with virtual disk and
using AIX native MPIO for a highly available rootvg. The system could be setup
and supported with physical adapters and disk.
Figure 2-4 Filesystems relationship from the Global Environment to the System WPAR
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30 Workload Partitions in IBM AIX Version 6.1
In this figure, box with a white background symbolize real filesystems, while box
with orange backgrounds symbolize links. The gray box labeled titian shows the
pathname of the filesystems as they appear to processes executing within the
system WPAR. The grey box labeled saturn shows the pathname to the
filesystems used within the global environments, as well as the basedir mount
point below which the system WPAR partition are created.
Example 2-1 shows the /wpars created within a global environment to host base
directory of WPARs created with the global environment.
Example 2-1 Listing files in the global environment
root: saturn:/ --> ls -ald /wpars
drwx------ 5 root system 256 May 15 14:40 /wpars
root: saturn:/ -->
Then when looking inside the directory of /wpars there is now the directory of
titian as show in Example 2-2.
Example 2-2 Listing /wpars in the global environment
root: saturn:/wpars --> ls -al /wpars
drwx------ 3 root system 512 May 1 16:36 .
drwxr-xr-x 23 root system 1024 May 3 18:06 ..
drwxr-xr-x 17 root system 4096 May 3 18:01 titian
In Example 2-3, we see the mount points for the filesystem of the operating
system of titian as created from saturn to generate this system WPAR.
Example 2-3 Listing the contents of /wpars/titian in the global environment
root: epp182:/wpars/titian --> ls -al /wpars/titian
drwxr-xr-x 17 root system 4096 May 3 18:01 .
drwx------ 3 root system 512 May 1 16:36 ..
-rw------- 1 root system 654 May 3 18:18 .sh_history
drwxr-x--- 2 root audit 256 Mar 28 17:52 audit
lrwxrwxrwx 1 bin bin 8 Apr 30 21:20 bin -> /usr/bin
drwxrwxr-x 5 root system 4096 May 3 16:41 dev
drwxr-xr-x 28 root system 8192 May 2 23:26 etc
drwxr-xr-x 4 bin bin 256 Apr 30 21:20 home
lrwxrwxrwx 1 bin bin 8 Apr 30 21:20 lib -> /usr/lib
drwx------ 2 root system 256 Apr 30 21:20 lost+found
drwxr-xr-x 142 bin bin 8192 Apr 30 21:23 lpp
drwxr-xr-x 2 bin bin 256 Mar 28 17:52 mnt
drwxr-xr-x 14 root system 512 Apr 10 20:22 opt
dr-xr-xr-x 1 root system 0 May 7 14:46 proc
drwxr-xr-x 3 bin bin 256 Mar 28 17:52 sbin
drwxrwxr-x 2 root system 256 Apr 30 21:22 tftpboot
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drwxrwxrwt 3 bin bin 4096 May 7 14:30 tmp
lrwxrwxrwx 1 bin bin 5 Apr 30 21:20 u -> /home
lrwxrwxrwx 1 root system 21 May 2 23:26 unix -> /usr/lib/boot/unix_64
drwxr-xr-x 43 bin bin 1024 Apr 27 14:31 usr
drwxr-xr-x 24 bin bin 4096 Apr 30 21:24 var
drwxr-xr-x 2 root system 256 Apr 30 21:20 wpars
Example 2-4 shows the output of the df executed from the saturn global
environment. It shows that one system WPAR is hosted within saturn, with its
filesystems mounted under the /wpars/titian base directory. The example shows
that the /, /home/ /tmp and /var filesystems of the system WPAR are created on
logical volumes of the global environments. It also shows that the /opt and /usr
filesystems of the WPAR are namefs mounts over the global environment /opt
and /usr.
Example 2-4 Listing mounted filesystem in the global environment
root: saturn:/wpars/titan --> df
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/hd4 131072 66376 50% 1858 6% /
/dev/hd2 3801088 646624 83% 32033 7% /usr
/dev/hd9var 524288 155432 71% 4933 8% /var
/dev/hd3 917504 233904 75% 476 1% /tmp
/dev/hd1 2621440 2145648 19% 263 1% /home
/proc - - - - - /proc
/dev/hd10opt 1572864 254888 84% 7510 4% /opt
glear.austin.ibm.com:/demofs/sfs 2097152 1489272 29% 551 1% /sfs
/dev/fslv00 131072 81528 38% 1631 16% /wpars/titian
/dev/fslv01 131072 128312 3% 5 1% /wpars/titian/home
/opt 1572864 254888 84% 7510 4% /wpars/titian/opt
/proc - - - - - /wpars/titian/proc
/dev/fslv02 262144 256832 3% 12 1% /wpars/titian/tmp
/usr 3801088 646624 83% 32033 7% /wpars/titian/usr
/dev/fslv03 262144 229496 13% 1216 5% /wpars/titian/var