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From Hari Kannan <>
Subject RE: [DISCUSS] Scaling up CPU and RAM for running VMs
Date Fri, 15 Feb 2013 00:12:44 GMT
Hi Nitin,

Please see below


-----Original Message-----
From: Nitin Mehta [] 
Sent: Tuesday, February 12, 2013 7:15 AM
To: Prashant Kumar Mishra;; Abhinandan Prateek
Cc: Chip Childers
Subject: Re: [DISCUSS] Scaling up CPU and RAM for running VMs

Apologize for the delayed response. Was involved in other issues.
Please find answers inline.

>-----Original Message-----
>From: Prashant Kumar Mishra []
>Sent: Thursday, January 24, 2013 12:26 PM
>Cc: Nitin Mehta
>Subject: RE: [DISCUSS] Scaling up CPU and RAM for running VMs
>Hi Nitin,
>I am planning to take the QA job for this feature. Have reviewed the 
>functional spec, gone through community discussion  and have the 
>following questions
>1-What is expected behavior of CS for Operating systems which do not 
>support dynamic scaling . ?

Will throw a not supported exception

Hari: How do we know which OS is supported or not? Is it going to be part of the "capabilities"
of hypervisor? Or where will this be specified/configured?
PS: I know we plan to implement this only on VMware for now, but when installed/shipped, how
will CS know the supported Hypervisor/OS?

>2-How much resources can be scaled up, is it limited by availability of 
>resource on host .?
>[Koushik Das ]
>"Having a range for CPU/RAM in compute offering is definitely another 
>way of doing it. But creating the higher limit would be tricky. I am 
>not sure if it is always known to users how much they want to scale up 
>to at the time of deploying VM. Moreover if the higher limit is known 
>then the VM can be deployed with that value itself. Also in case of 
>having a range in the offering the usage part needs to be handled 
>appropriately. Currently usage is purely based on the offering and 
>individual values are not stored".
>[/Koushik Das]

It is not limited by the resources on host but on the available capacity in any of the host
within the cluster.

Hari: I'm not sure I understand the question - how is this any different than requesting a
new VM? Or upgrading from offering A to Offering B that exists today (although VM needs to
be shutdown)?

>it seems  its totally depend on service offering , please correct me if 
>I am wrong.
>3-  Scheduled snapshot of volumes during the operation .
>For vmware, the entire vm is locked by HV and this can be an issue. I 
>will leverage on current implementations for existing interactions like 
>scheduled snapshots events during live migration and will replicate the 
>Can you elaborate what is expected in case of VMware .

What I mean is there is an existing functionality which is implemented the same way. I will
just do it the same way.

>4 - what is expected behavior in case of  powers off the vm during the 
>operation .? is it different for different hypervisors.?

There is nothing much to do for powered off vms because we will just update the DB. When the
vm is started it will pick up these values from the DB.
This functionality already exists.

>5- what is expected in case of migration fails( In FS no description 
>about this),
>       -CS will  retry to migrate it again if yes how many time ?
>      - will it mark as a failure and can't  scale up(even resources 
>are available in cluster) ?

We will retry N (configurable) times and if unsuccessful we will throw an exception to the

Hari: Can you please elaborate why a migration might fail? And, is the "N" configurable times
a new global?

>6- Apart from  "scaleVirtualMachine"    any other APIs are getting
>changed ?


>7-Scale down is allowed ? (still open issue in FS)

No for time being. 

>8-Are we going to introduce custom compute offering (still open issue 
>FS) ?

No for now 

>9- what are the guide line for upgrade  ?

There is nothing for upgrade because we do not introduce new values in DB.

>10-Any DB changes ?

See #9 above.

>11- which Usage events are getting introduced for billing .?

Will update the FS.

>12-hypervisor support ,is it only for VMware (as per FS)  or its 
>getting extended for XS/KVM also ?

There are subtasks opened for XS and KVM. I am doing it only for Vmware.

>Prashant Kumar Mishra
>-----Original Message-----
>From: Koushik Das []
>Sent: Saturday, December 15, 2012 11:14 PM
>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.

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