Open Stack

In Nova, "ram_allocation_ratio" & "reserved_host_memory_mb" are not 
mutually exclusive options, so they work together [0].

If it make sense or not to use "ram_allocation_ratio != 1" when 
"reserved memory != 0" is up to the cloud admin (depending on your use 
case, the purpose of your cloud, the underlying hypervisor you're using, 
etc...)

Cheers,
Luis

[0] 
https://github.com/openstack/nova/blob/master/nova/scheduler/filters/ram_filter.py#L53

On 11/28/2014 12:50 PM, mad Engineer wrote:
> Excellent answer thank you sir.
> One doubt comes into my mind is for this reservation to work RAM over
> committing should be disabled?
> ie ram_allocation_ratio=1
> Thanks for your help
>
>
> On Thu, Nov 27, 2014 at 7:20 PM, Luis Fernandez Alvarez
> <luis.fernandez.alvarez at cern.ch> wrote:
>> Hi,
>>
>> In general, you can see 'reserved_host_memory_mb' as your estimation of how
>> much memory your hypervisor needs. From the point of view of Nova, your
>> system is consuming the amount you set in 'reserved_host_memory_mb' [0].
>>
>> Then, the field 'free_ram_mb' (the one that is checked when VMs are being
>> scheduled) is calculated using the memory consumed by the instances and the
>> value of reserved memory [1].
>>
>> Said that, the scheduler won't see the real free mem (700Mb in your case),
>> it will see the calculated value. I would suggest you take a look to the
>> value of "free_ram_mb" on your hypervisor (the value in the database: like
>> "nova hypervisor-show", not the one in the compute logs), and then... you
>> compare. If you're expection 700Mb and you see 900Mb, you should tweak a bit
>> more your 1024Mb or reserved memory and increase it.
>>
>> It's a bit difficult to follow the flow in the code, but these links are
>> quite useful to understand how it works.
>>
>> [0]
>> https://github.com/openstack/nova/blob/master/nova/compute/resource_tracker.py#L695
>> https://github.com/openstack/nova/blob/master/nova/compute/resource_tracker.py#L708
>> [1]
>> https://github.com/openstack/nova/blob/master/nova/compute/resource_tracker.py#L532
>>
>>
>>
>> On 11/27/2014 01:55 PM, mad Engineer wrote:
>>> it reports "Free ram (MB): 425"
>>> but free -m has different result.
>>>
>>> Is it working for you.Are you using icehouse
>>>
>>> On Thu, Nov 27, 2014 at 6:16 PM, George Mihaiescu <lmihaiescu at gmail.com>
>>> wrote:
>>>> Then I would enable debug and verbose in nova.conf and restart the
>>>> scheduler
>>>> service. In this way you should see in the logs the entire scheduler
>>>> logic
>>>> and what resources it thinks your host has.
>>>>
>>>> On 27 Nov 2014 06:20, "mad Engineer" <themadengin33r at gmail.com> wrote:
>>>>> George,
>>>>>                 overcommit of RAM is 1  and that is working.However
>>>>> instances are still getting created with available free memory <
>>>>> reserved_host_memory_mb
>>>>>
>>>>> On Thu, Nov 27, 2014 at 4:33 PM, George Mihaiescu <lmihaiescu at gmail.com>
>>>>> wrote:
>>>>>> Depending on your overcommit ratio, the scheduler can schedule
>>>>>> instances
>>>>>> using more virtual memory than the available physical memory on the
>>>>>> host,
>>>>>> 700 MB in your case.
>>>>>>
>>>>>> On 27 Nov 2014 05:36, "mad Engineer" <themadengin33r at gmail.com> wrote:
>>>>>>> hi all i have set
>>>>>>> reserved_host_memory_mb in nova.conf of controller and compute and
>>>>>>> restarted necessary services.
>>>>>>> i am expecting scheduler to not pickup host that has less than what is
>>>>>>> reserved_host_memory_mb
>>>>>>> in my example i put reserved_host_memory_mb = 1024
>>>>>>> and free RAM in compute node is 700 Mb.
>>>>>>> But still scheduler chooses this host and created a new instance on
>>>>>>> it.I
>>>>>>> am expecting scheduler to show "No valid Hosts found" as it has less
>>>>>>> ram
>>>>>>> than reserved_host_memory_mb = 1024
>>>>>>>
>>>>>>> Can some one help me understand this value
>>>>>>>
>>>>>>> Thanks
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Mailing list:
>>>>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
>>>>>>> Post to     : openstack at lists.openstack.org
>>>>>>> Unsubscribe :
>>>>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
>>>>>>>
>>> _______________________________________________
>>> Mailing list:
>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
>>> Post to     : openstack at lists.openstack.org
>>> Unsubscribe :
>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
>>
>>
>> _______________________________________________
>> Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
>> Post to     : openstack at lists.openstack.org
>> Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack