[Users] Guests accessing multiple host disks in oVirt

[Itamar Heim]

On 06/01/2012 08:26 PM, Oded Ben Ozer wrote:
> Hi Itamar,
>
> Local storage, my plan is use the local disks in each hypervisor (4 or 6
> depending on generation, no HW raid ) to get cheap, none-centralized
> high IO storage for my VMs.
> For example :
> A Cassandra/Hadoop VM would get 6 disks and would use RAID0 to maximize
> IO performance and rely on Cassandra architecture for redundancy.
> A MySQL VM running on the same hypervisor would use RAID10 on its 6
> disks to balance IO performance and redundancy.
> A third VM running our in house web scraping software would only use two
> disks (RAID1) but consume most of the hypervisor CPU and RAM.
>
> This is more or less how we run stuff currently, using XEN community,
> but after passing the 100 hypervisors mark some sort
> of centralized management is becoming necessary.
>
> If this is not possible using the web UI it might be possible by editing
> the templates that generate the libvirt VM XML.

sounds a bit elaborate to me rather than having the disks used as one or 
at most two sets of disk, but sounds like you've done your math.

if you want to expose a guest disk from a specific storage, you would 
need to create a storage domain from that storage (either block based or 
FS based).

so, for simple file based local storage, you would need to mount and 
create a path with proper vdsm permissions on the host for each of these 
disks.
then you can choose per VM to add disks to it from which ever storage 
domains you want

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> On Fri, Jun 1, 2012 at 5:34 PM, Itamar Heim <iheim at redhat.com
> <mailto:iheim at redhat.com>> wrote:
>
>     On 05/31/2012 05:12 PM, Oded Ben Ozer wrote:
>
>         Hi folks,
>
>         I'm trying to evaluate ovrit as a possible virtualization
>         solution for
>         my datacenter .
>         I need  some of my VMs to have access to multiple disks
>         installed in the
>         host  so that the RAID  will be configured in the guest level,
>         this way
>         I can optimize redundancy and  /IO performance per guest. (raid0 vs
>         raid10 vs raid 5) - this would be  similar to what EC2/Openstack
>         call ephemeral storage.
>         Is this possible in oVirt  ?
>         A less desirable solution would be to create different RAID
>         arrays in
>         the host and place VM images on different arrays, is that possible ?
>           ( according to the pdf guide this is possible in RHEL but not
>         in oVirt
>         node ?!? )
>
>
>     can you please elaborate a bit more on your use case?
>     specifcially, are you planning on using shared storage
>     (fc/iscsi/nfs/gluster/etc.) or local storage of each hypervisor?
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> --
> Oded Ben Ozer
> IT Operations Architect
> Pageonce inc
> +972544668357
>