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From Nitin Mehta <Nitin.Me...@citrix.com>
Subject Re: [DISCUSS] Scaling up CPU and RAM for running VMs
Date Tue, 18 Dec 2012 07:57:02 GMT

On 18-Dec-2012, at 8:54 AM, Mice Xia wrote:

> Great feature and I believe a lot of customers need it, hope Xenserver will support dynamic
memory change one day.
> 
> [Koushik]
> Assuming that in the updated compute offering only CPU and RAM has changed, the deployment
planner can either select the same host in which case the values are dynamically scaled up
OR a different one in which case the operation fails. In future if there is support for live
migration (provided HV supports it) then another option in the latter case could be to migrate
the VM first and then scale it up.
> [/Koushik]
> 


Mice - Great point. But, I think when the vm is scaled up, allocators need to be wise enough
to figure out if it could be adjusted on the same host or need live migration. I think atleast
XS and Vmware support live migration (across clusters as well) now so dynamic scaling would
have less probability of failing, but this could be an expensive operation because migrating
volumes across clusters will be resource intensive.

> For VMware, it supports memory overprovisioning, which means the total size of VM's allocated
memory can be larger than host's physical memory. Maybe we can leverage it and reduce the
chance to migrate VM before scale up.
> 
> 
> Regards
> Mice
> 
> -----Original Message-----
> From: Koushik Das [mailto:koushik.das@citrix.com] 
> Sent: Sunday, December 16, 2012 1:44 AM
> To: cloudstack-dev@incubator.apache.org
> Subject: [DISCUSS] Scaling up CPU and RAM for running VMs
> 
> Currently CS supports changing CPU and RAM for stopped VM. This is achieved by changing
compute offering of the VM (with new CPU and RAM values) and then starting it. I am planning
to extend the same for running VM as well. Initially planning to do it for Vmware where CPU
and RAM can be dynamically increased. Support of other HVs can also be added if they support
increasing CPU/RAM.
> 
> Assuming that in the updated compute offering only CPU and RAM has changed, the deployment
planner can either select the same host in which case the values are dynamically scaled up
OR a different one in which case the operation fails. In future if there is support for live
migration (provided HV supports it) then another option in the latter case could be to migrate
the VM first and then scale it up.
> 
> I will start working on the FS and share it out sometime next week.
> 
> Comments/suggestions?
> 
> Thanks,
> Koushik


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