Virtualization and memory

[abc]

Hi,
Am I correct in thinking that memory can't be shared and is always dedicated to an LPAR, even in a virtualized, micro-partitioned environment?
Thanks.

[John R Peck]

Once it's in use, I would hope so, otherwise it's a major security violation (like a "segmentation violation" but between LPARs instead of processes) !  Of course you can dynamically move and reassign the RAM (after it's cleared from any use).

[Mark Taylor]

AMS .. Active Memory Sharing ..

Ref: http://www.ibm.com/developerworks/aix/library/au-pwr6_ams/index.html?ca=dgr-lnxw03POWER6-AMSdth-A&S_TACT=105AGX59&S_CMP=grlnxw03

HTH
Mark Taylor

[Michael]

Thanks Mark, I should have "corrected" that long ago.

In short, POWER6 and POWER7 processors can be setup to share memory, similar to sharing processor cores. The Hypervisor ensures that memory is scrubbed before it ias accessed by another partition.

New in Power7 is a feature called Active Memory Expansion, or AME. AME is quickly being seen as a cost-saving benefit, but it remains a trade-off between adding more physical memory and using (underutilized) processor cycles.