GordonLiq
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Hyper V Live migration with limited Memory
Hi,
I have 2 Hosts install Hyper V 2008 R2 and clustered.
both Host with 12G memory.
if I have 2 VMS running on each Host , and each one configured with dynamic memory 2G-6G.
when they runing normal , each Host have 10G used , each vm used 5G realy memory.
in this case , if one of the host dead , can VMS be live migrated to another Host?
if they all use the minimun , then total 8G memory , it should works , but the real memory used is 10G each and that will not enough .
I have 2 Hosts install Hyper V 2008 R2 and clustered.
both Host with 12G memory.
if I have 2 VMS running on each Host , and each one configured with dynamic memory 2G-6G.
when they runing normal , each Host have 10G used , each vm used 5G realy memory.
in this case , if one of the host dead , can VMS be live migrated to another Host?
if they all use the minimun , then total 8G memory , it should works , but the real memory used is 10G each and that will not enough .
ASKER
when you said failed, is it different to just restart or shundown?
I have tried with the enough free memory , the VM can be live migration (High availability) to another Host, dont know why you said no.
the option of this is I dont want to leave the free memory on each host to be able to HA, I would like to set the dynamic for each VM (half -full) so that physical memory will always been efficient used.
I have tried with the enough free memory , the VM can be live migration (High availability) to another Host, dont know why you said no.
the option of this is I dont want to leave the free memory on each host to be able to HA, I would like to set the dynamic for each VM (half -full) so that physical memory will always been efficient used.
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ASKER
If there is insufficient memory available to migrate it, the guest OS is placed in a save state and becomes unusable until the cluster finds enough resources on a host to bring it back up.
this is the answer I looking for
this is the answer I looking for
I should point out though that "Live Migration" when a node fails is impossible - because the node is dead.
If the network is lost, the cluster that does not host the quorum disk will be kicked out the cluster. It has no way to migrate from one host to another (network lost), so the virtual machine is just stopped, and the surviving node has to start it up from scratch, meaning that the startup memory is used.
Similarly, if the disk is lost, the cluster that does not host the quorum disk will be kicked out of the cluster. It has no way to save the virtual machine state to disk (disk lost), so the virtual machine is just stopped,and the surviving node has to start it up from scratch, meaning that the startup memory is used.
You may end up with an issue if 2 of the virtual machines on the surviving node are both using their maximum amount of memory - then there are no resources for the failed virtual machines to start up. I'd highly advise to increase the memory of all of your hosts so that it can cope with the maximum amount of allocated memory. You should never over-commit a cluster - always have enough resources available to cope with a complete node failure.