[ovirt-users] Storage questions

[Oscar Segarra]

>
> Hi,
>
> As on oVirt is it possible to attach local storage I supose it can be used
> to run virtual machines:
>
> I have drawn a couple of diagrams in order to know if is it possible to
> set up this configuration:
>
> 1.- In on-going scenario:
> Every host runs 100 vdi virtual machines whose disks are placed on local
> storage. There is a common gluster volume shared between all nodes.
>
> [image: Imágenes integradas 1]
>

With local storage you end up losing many of the benefits of shared storage
- including migration and HA.
If you do have SSD on your physical hosts, have you considered building
gluster volume using these? This could give you improved performance.
Regarding performance, I think it is best that you run a test comparing
gluster storage performance with local storage and see if this is
acceptable to you. Please share the results in case you do.

Yes, but I want to avoid possible corruption problems due to possible
unrecoverable gluster bugs.
We have to make some developement and I don't want to spend money in this
process and then discover that the performance is not good enought and have
to do a

In the above diagram each host is in its own cluster - as all hosts in a
cluster should have access to the storage domain?

Yes, every host has ho have access to two storage domains: The local one
and the shared gluster one.

Is the gluster volume for backup served from a separate set of server?

No, each host will have 2 disks /dev/sdb1 (for runing vm on local storage)
and /dev/sdc1 (for shared gluster where store backups)


>
> 2.- If one node fails:
>
> [image: Imágenes integradas 2]
>
> oVirt has to be able to inventory the copy of machines (in our example
> vdi201 ... vdi300) and start them on remaining nodes.
>
> ¿Is it possible to reach this configuration with oVirt? ¿or something
> similar?
>

This is the use case for gluster volume shared storage - where volume is a
replica 3. If any host goes down, the data is available on the remaining 2
nodes, and the VMs can be migrated to other nodes.

Yes, I know, but I'm already worried about corruption issues due to
possible gluster bugs or performance problems under heavy load.

I don't think what you ask for is possible automatically. If you want local
storage to gluster volume backup, you would need 1-1 mapping. i.e each
local storage domain has its own gluster volume backup.You could then
import the storage domain that's backed up on the gluster volume and start
the VMs on the remaining hosts.

I don't want local storage for backup, I prefer gluster shared storage for
backup.


> Making backup with the import-export procedure based on snapshot can take
> lot of time and resources. Incremental rsync is cheaper in terms of
> resources.
>

Geo-replication based backup internally uses rsync, it also takes into
account that VM images are consistent on disk before being synced. It
however works as a backup option between two gluster volumes.

Do you know if is it possible to have multiple masters geo-replicating
against a single slave?

Thanks a lot.
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