[Users] oVirt 3.1 and Glusterfs how-to

[Itamar Heim]

On 07/05/2012 12:20 AM, Robert Middleswarth wrote:
> I wrote a basic how to for using glusterfs under oVirt.  If you have any
> questions or you find mistakes please let me know.
>
> Thanks
> Robert
>
> http://www.middleswarth.net/content/installing-ovirt-31-and-glusterfs-using-either-nfs-or-posix-native-file-system
>
>
>
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> oVirt 3.1 is currently in beta and compared to 3.0 it adds a several new
> features. One of the nice new features is glusterfs support. For it
> intended use it works well but I personally think it needs to be
> adjusted to for more generic use. The 2 main limits that effect me are.
> 1) Only oVirt nodes in the same cluster can be used as bricks to create
> clusters. So you can't add in storage only nodes in the same oVirt
> cluster as nodes. However you can create a cluster of just gluster only
> nodes.

the long term plan would be "dynamic clusters/services" - a subset of 
hosts with gluster, a subset of hosts with virt, some with both, in 
overlapping clusters.
a more simple solution to this would be just allowing to specify at host 
level if to use the host for gluster service and/or virt service (so 
still same set of hosts in a cluster, just allowing to choose if they 
are to be used for the relevant service).

 > 2) You can not change what interface / IP gluster uses, it will
> always use the ovirtmgmt network. This is a weakness as many people have
> an independent network just for storage and they can't use them with 3.1.

sorry, i don't understand this one - only the management of gluster is 
done via this interface. you can define a different logical network in 
the cluster for storage, configure ip addresses for them, and define the 
mount point that way.
(well, apart from potential bugs on network definitions in 3.1 which may 
still exist)

>
> If you can live with these limits then gluster intergration is for you.
> Before we start you should ask yourself whether you want to use
> glusterfsover NFS or posix (Native) fs. Both work and are very simlilar
> in setup but they do work slightly differently. Many prefer the native
> version and if you are using Fedora 17 with it latest kernal then native
> (posix) fs actually supports direct IO that will increase the throuput a
> lot. However I found on CentOS 6.2 nodes NFS ran faster because NFS
> shares are cached. My testing was over a 1G networks so a faster network
> will yield different results. Both install methods are pretty much the
> same I will add notes on there differences.

cache is supposed to be only relevant to read only images like 
templates, and i'm not even sure this optimization is in.
so caching is supposed to be disabled (otherwise, shared disk won't 
work, etc.)
maybe something else?

>
> A quick word about OS. While there are plans to support EL6 and other
> Linux based distributions, support is currently limited to Fedora 17.
> However Andrey Gordeev ( http://www.dreyou.org/ovirt/ ) has created EL6
> packages. Since Fedora 17 crashes on both my Dells every 10 to 12 hours
> I use the centos builds right now. Although the CentOS builds work
> really well there are a few missing features, such as live snapshots. I
> have done both installs and the steps outlined below work for both.
>

very nice!