DRO with Dynamic Capacity on Demand
Capacity on Demand (CoD) from IBM®
Systems is a powerful tool that activates unused cores or mobile memory for a host,
giving it more computing power or memory instantly. On eligible
systems, the PowerVC
Dynamic Resource Optimizer (DRO) works with CoD to relieve overburdened
systems much more quickly than when it has to migrate virtual machines to balance system usage. For
more information about CoD, see
Capacity on Demand.
OverviewWhen DRO and CoD work together, DRO has the following additional capabilities:
- DRO detects changes in your Enterprise Pool definitions and periodically updates them in PowerVC, even if the Enterprise Pool license is purchased after PowerVC was set up.
- DRO uses free CoD mobile cores to automatically ease the workload on busy hosts.
- DRO activates mobile memory to make more space available to overburdened hosts.
Example: Mobile core activation
Activating mobile cores
- You cannot activate more mobile cores than the total number of physical cores on the machine. Therefore, the host must have at least one inactive core to be able to move a mobile core to it.
- If mobile cores are removed from a server but it cannot reclaim the cores because they are being
used, they become unreturned cores.
- DRO tries not to create unreturned cores. However, under certain circumstances, such as out-of-band operations, DRO operations might result in unreturned cores. In this case, DRO tries to detect and return the unreturned cores.
- DRO does not use CoD operations if the host has any unreturned cores.
Activating mobile memory
When enabled, DRO tries to claim available mobile memory from an Enterprise Pool and activate that memory on violated hosts. If there is no memory available in the pool, DRO reclaims memory from other unviolated NovaLink managed hosts and returns it to the pool for use by the violated host. However, memory is not reclaimed if doing so would exceed the memory threshold for that host. Additionally, mobile memory is never reclaimed from HMC managed hosts. If a threshold cannot be satisfied by mobile memory operations, DRO migrations will occur instead, assuming they are enabled.