[one-users] Open Nebula, NFS and requirements of disk space?

[Rogier Mars]

Hi, 

There are a couple of variables to take into account when planning your storage requirements. When you choose a shared storage setup (e.g. with NFS) you need to make sure that it is big enough to hold the "golden images" and all the running images. But size of the storage is not the only parameter. You should also make sure the performance of the storage is sufficient. When you run 15 VM's and the disk images are stored on a single 500GB disk, this disk will become the bottleneck and the VM's will perform badly. This will show in high I/O wait within the VM's. 

When you choose to use a non shared setup (e.g. copy the images via SCP) you only need the space for the golden images in the repositories, provided that you don't want to store stopped images and be able to restart perviously stopped images. The cloud hosts need as much storage as the number of VM's they will run. 

The two storage backend have different characteristics. Shared storage allows you to do live migrations and directly start non-cloned images. Non-shared storage is more scalable as the NFS share is not the bottleneck, but you can't do live migrations. 

Best regards, 

Rogier

On May 16, 2011, at 4:58 PM, Steffen Neumann wrote:

> Ah,
> 
> now I get the idea: the golden images are on the headnode, 
> exported to the worker nodes via NFS, and then they're 
> cloned onto the local worker disk drives with 36GB. 
> Did I get that right ?
> 
> Now, speed-wise the only benefit would be if NFS 
> gets the image to the worker nodes faster over the network than 
> copying via ssh / scp. Which, I think, is only 
> a few percent, if at all. The images definitely 
> need to be copied fully, because each node needs
> its own copy. If all used the same image, the filesystem 
> would go up in smoke if two nodes write to it 
> without knowing about each other...
> 
> So yes, it might be possible, but IMHO does not make 
> a lot of sense. 
> 
> Or did I misunderstand anything ?
> 
> Yours,
> Steffen
> 
> 
> On Mon, 2011-05-16 at 15:25 +0200, Anders Branderud wrote:
>> He thinks it is a faster solution - i.e. with NFS all of the image
>> doesn't necessarily need to be copied from the front end to the worker
>> node, but only the parts that the user needs. Thus it can be more
>> efficient.
>> "SSH Non shared" requires the image file to be cloned to all VM's,
>> which in many cases is unnecessary and isn't efficient.
>> 
>> 
>> Regards, Anders
>> 
>> 2011/5/16 Steffen Neumann <sneumann at ipb-halle.de>
>>        On Mon, 2011-05-16 at 13:48 +0200, Anders Branderud wrote:
>>> Hello!
>>> Thanks Steffen!
>>> 
>>> Yes, I am aware of the "Non-Shared - SSH"-solution.
>>> However, the person that I am doing my thesis for, want it
>>        to be done
>>> with NFS.
>> 
>>        What does he want on NFS ?
>> 
>>        Gruss,
>> 
>>        Steffen
>> 
>>        --
>>        IPB Halle                    AG Massenspektrometrie &
>>        Bioinformatik
>>        Dr. Steffen Neumann          http://www.IPB-Halle.DE
>>        Weinberg 3                   http://msbi.bic-gh.de
>>        06120 Halle                  Tel. +49 (0) 345 5582 - 1470
>>                                         +49 (0) 345 5582 - 0
>>        sneumann(at)IPB-Halle.DE     Fax. +49 (0) 345 5582 - 1409
>> 
>> 
>> 
>> 
>> 
>> 
>> -- 
>> Kind Regards, Anders Branderud
>> 
>> [Personal blog] bloganders.blogspot.com  : Logical reasons - based on
>> scientific premises - for the existence of a Creator and that He
>> hasn't left His sapient creatures without an Instruction Manual -
>> Torah ['books of Moses'] - to ascertain, and aspire to, His purpose.
>> 
>> [Company] Anders Branderud IT Solutions - www.abitsolutions.org
>> 
> 
> -- 
> IPB Halle                    AG Massenspektrometrie & Bioinformatik
> Dr. Steffen Neumann          http://www.IPB-Halle.DE
> Weinberg 3                   http://msbi.bic-gh.de
> 06120 Halle                  Tel. +49 (0) 345 5582 - 1470
>                                  +49 (0) 345 5582 - 0
> sneumann(at)IPB-Halle.DE     Fax. +49 (0) 345 5582 - 1409
> 
> 
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