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Is Dynamic Memory Control (DMC) reliable enough for production ?

Lv Joe




We have a bunch of servers running with XenServer 7.1CU2.   To allow users to create more VMs even when host is full,  we are evaluating the Dynamic Memory Control (DMC) feature. 


In our testing environment with DMC enabled,  each host is running out memory (all has been allocated),  and  we ran app 'memtester' on VMs to completely utilize all allocated VM memory , then we tried to create one more extra VM on that host. 


Due to DMC,  the existing running VMs reduced their memory to make room for the new VM, and the new VM was successfully created without issue.   However,  we noticed the memory stress testing tool 'memtester'  running within those VMs were all terminated due to the memory change.   It brings the concern that if DMC would possibly cause production applications 'killed' while VM's memory shrinks ?


Any idea about the DMC reliability in real production environment ?  anything we need pay attention to if put DMC in production ?


Thanks a lot in advance !


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Absolutely! Have been running this way for years. It's especially useful when doing updates and needing to move VMs from one host to others so the one host can be rebooted. For smaller pools, there may not be quite enough space to accommodate all VMs if one or more of the hosts are down and this is one way to circomvent that limitation.


You should test what is sufficient to run a VM, of course, and pick your minimum memory configuration accordingly. Above all, you don't want to run out of swap space by shrinking the memory down too far. As with anything like this, testing ahead of time is always an important part of the process.



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