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