[Ovirt-devel] I need oVirt!

[Daniel P. Berrange]

On Tue, Mar 11, 2008 at 09:30:36AM -0400, Mark Nielsen wrote:
> Greetings,
> 
> I had a chat in #ovirt on freenode and was asked to provide some details
> on what I need oVirt to do, and I'm adding what I can offer in way of
> helping it get there.
> 
> My environment consists of 3 8 nodes clusters. These 8 dom0s are Dell
> 2950's. They have 2x 2Gb Qlogic FC HBAs to both 3Par and EMC SANs which
> are multipathed using dm-multipath. Networking is done through 2 copper
> and 2 fiber NICs. The 2 copper are bonded (mode 0, "flat" non-routed
> private network for Cluster Suite comms) and the 2 fibers are bonded
> (mode 4, VLANs galore, multiple Xen bridges.. up to 10 at this point
> with more planned). These 8 nodes are clustered together using Cluster
> Suite which is primarily used to run the VMs as services for failover.
> GFS is used, but only for a common /etc/xen so the VMs can be started
> from any cluster node. The VM storage comes from logical volumes (clvmd
> running).

So would this be a fair summary of your networking setup:

 eth0 + eth1 -> bond0    (cluster suite / management)
 eth2 + eth3 -> bond1    (guest connectivity)

 bond1.1 + br01  => Bridged VLAN 1  (guest lan)
 bond1.2 + br02  => Bridged VLAN 2  (guest lan)
 bond1.3 + br03  => Bridged VLAN 3  (guest lan)
 bond1.4 + br04  => Bridged VLAN 4  (guest lan)
 bond1.5 + br05  => Bridged VLAN 5  (guest lan)

> 1) I need oVirt to support the fiber channel HBAs to the SAN so I can
> continue to use logical volumes for the domUs

We are currently only supporting iSCSI, but direct attached storage is the
next thing on the feature list for storage support. This is pending HBA
support in libvirt - reasonably straightfowrad todo. Once this is done, then
LVM is the logical next step. 

Can you describe in more detail the way you carve up your storage ?  The
relationship between LUNS, volume groups and guests ?  1 LUN + VG per
guest, or many LUNs in 1 VG, split across many guests, or something else ?
Also, do you use multipathing or RAID at all ?

> 2) I'm using RHEL 5.1 and need to make sure oVirt plays well with Xen.

For the guest that should not be a problem. oVirt is using KVM fullvirt
which can run more or less any guest. There are now paravirt drivers
available for KVM backported to 2.6.18. Or alternatively there is Xenner
which lets us run Xen paravirt guests in KVM.

For managed nodes (ie where the guests run) we provide a Fedora 8 based 
stateless image, but the core requirement is basically libvirtd daemon
version 0.4.1 or later, so that can be built around other OS if needed.

> 3) My guests are currently services of Cluster Suite, I'm hoping that
> oVirt will play well with Cluster Suite as well as Conga...

So, this is clustering at the physical host level ? ie if a physical
host dies, cluster suite moves all your VMs to another host ? If so,
that is definitely something on our roadmap. We won't neccessarily use
Conga for this - we may integrate the low level clustering infrastructure
directly into the oVirt images.

For clustering inside the guest, we're intending to work with the cluster
guys to provide some form of generic fence device to all guests. The goal
is to allow the guest administrator to setup clustering of services inside
their guests without needing co-ordination with the host admin.

> I think oVirt is what I'm looking for to manage my VMs and hosts, but
> please feel free to wave your hand in front of my face and tell me if
> this is not the tool I'm looking for.

oVirt is at  a very early stage of development, so as you can see we can't
currently meet all your feature requests yet. Everything you mention is
definitely on our roadmap - you outline precisely the kind of deployment
scenarios we want & need to be able to handle.

Regards,
Dan.
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