XEN Memory Overcommitment
Overview
The xnCORE - xn-mem-daemon offers the possibility to dynamically distribute the memory of your physical open source Xen server. The special feature: the memory can be overbooked. You can define a guaranteed minimum and maximum memory for each virtual server or the global system. The xnCORE - xn-mem-secure daemon will ensure that the required memory is allocated. If more memory is required in sum than installed in the physical system the xnCORE - xn-mem-daemon will ensure a fair compromise in memory distribution. With an overbooked system the sum of the minimum configured memory must not exceed the physical systems memory for the xnCORE - xn-mem-daemon to start and work correctly.
The xnCORE - xn-mem-daemon requires data on the current memory usage from each virtual server. Therefore the xnCORE - xn-client has to be installed on each virtual server. If this is not installed or disabled, the client gets only the minimum memory defined.
Example
The following example will show how the xnCORE - xn-mem-daemon assigns memory to a virtual server dynamically. For the example a minimum memory of 256MB was configured for the virtual server:
The following scheme which was generated by xnCORE - xn-mon shows how the xnCORE - xn-mem-daemon distributes the memory as it is required. The assigned memory will not fall below the minimum configured value.
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