Chapter 3. Virtualization 95
3.3.6 Active Memory Sharing
Active Memory Sharing is an IBM PowerVM advanced memory virtualization technology that
provides system memory virtualization capabilities to IBM Power Systems, allowing multiple
partitions to share a common pool of physical memory.
The physical memory of an IBM POWER6 or POWER7 System can be assigned to multiple
partitions either in a dedicated or in a shared mode. The system administrator has the
capability to assign physical memory to a partition and physical memory to a pool that is
shared by other partitions. A single partition can have either dedicated or shared memory.
In a dedicated memory model, the system administrator’s task is to optimize available
memory distribution among partitions. When a partition has performance degradation due to
memory constraints and other partitions have unused memory, the administrator can allocate
memory by doing a DLPAR operation.
In a shared memory model, it is the system (PowerVM Hypervisor) that automatically decides
the optimal distribution of the physical memory to partitions and adjusts the memory
assignment based on partition load.
Active Memory Sharing can be exploited to increase memory use on the system either by
decreasing the system memory requirement or by allowing the creation of additional
partitions on an existing system.
Figure 3-8 shows each logical partition can be configured to have shared memory using
Active Memory Sharing or dedicated memory.
Figure 3-8 Active Memory Sharing block diagram with shared and dedicated memory
Note: Active Memory Sharing is only available with the Enterprise version of PowerVM.
MEMORY
LPAR #1
Shared Memory
Pool
PowerVM Hypervisor
Virtual I/O
Server
LPAR #2
Dedicated
Memory
LPAR #4 LPAR #3
LPAR # 2
LPAR #1
Dedicated
Memory
LPAR #5
AMS
Hdisk
Hdisk
Paging
Devices
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