Specifications

VMware and BEA WebLogic Solutions Deployment Guide
145
Appendix A: VMware Migration for a BEA WebLogic
Application Server Virtual Machine
Moving a virtual machine from one host to another is called migration. Migrating a powered-on virtual
machine is called “Live migration with VMotion”. Migration with VMotion, designed to be used between
compatible systems, allows you to migrate virtual machines with no downtime and zero disruption to end
users but requires VMotion licensing and specific configuration.
You can perform the following types of migration of virtual machines (VM):
1. Cold Migration: VM Migration in powered-off or suspended state.
a. If the VM files are on Shared storage (SAN, iSCSI or NAS), only configuration files are
moved with no disk movement.
b. Relocation: When VM files are not on SAN (Ex: local storage) and needs to be moved to
another storage destination or ESX Server host.
2. Live Migration with VMotion: Moving a virtual machine that is powered on with online applications.
The VM files should be located on shared storage and accessible by both the source and
destination ESX Server hosts.
VMotion allows working processes to continue throughout the migration process. The entire state of the
virtual machine as well as its configuration file, if necessary, are moved to the new host even while the data
storage remains in the same location on the SAN. The associated virtual disk remains in the same location
on the SAN storage that is shared between the two hosts. Once the configuration file is migrated to the
alternate host, the virtual machine runs on the new host.
The state information includes the current memory content and all the information that defines and identifies
the virtual machine. The memory content includes transaction data and whatever bits of the operating
system and applications are in the memory. The defining and identification information stored in the state
includes all the data that maps to the virtual machine hardware elements, such as BIOS, devices, CPU,
MAC addresses for the Ethernet cards, chip set states, registers, and so forth.
Migration with VMotion takes place in 3 distinct stages:
1. When Migration with VMotion is requested, VirtualCenter verifies that the existing VM is in a stable
state with its current host.
2. The VM state information (memory, registers, network etc.) is copied to the target host.
3. The VM resumes its activities on the new host.
If any error occurs during migration, the virtual machines revert to their original states and locations.
Virtual machines can be moved between hosts within the same datacenter. Virtual machines cannot be
moved between datacenters.
The VMkernel networking stack must be set up properly to accommodate VMotion.
The network services provided by the VMkernel (iSCSI, NFS, and VMotion) use a TCP/IP stack in the
VMkernel. This TCP/IP stack is completely separate from the TCP/IP stack used in the service console.
Each of these TCP/IP stacks accesses various networks by attaching to one or more port groups on one or
more vSwitches.
VMotion Requirements
Shared Storage
Ensure that the managed hosts use shared storage. Shared storage is typically on a storage area network
(SAN), but can also be implemented using iSCSI and NAS shared storage.
CPU Compatibility
Make sure that the source and destination hosts have a compatible set of processors.
VMotion transfers the running architectural state of a virtual machine between underlying VMware ESX
Server systems. VMotion compatibility requires that the processors of the target host be able to resume
execution using the equivalent instructions that the processors of the source host were using when
suspended. Processor clock speeds and cache sizes, and the number of processor cores may vary, but