[PVE-User] Proxmox VE Clustering Usage Scenarios

[Martin Maurer]

> Subject: [PVE-User] Proxmox VE Clustering Usage Scenarios
> 
> Hi all,
> 
> It's state very clearly around the VE wiki that the child nodes must be
> empty (no VM's, no templates, etc) when they are connected to master.
> This makes sense, VMID conflicts are bad.  I'm trying to understand a
> little more about the nuances of clustering so that I can have a plan if
> things go awry - and to have more things to share when trying to
> convince people to use Proxmox VE :).
> 
> I'm hoping that the user community might be able to share some of their
> own experiences to help current and future Proxmox VE users with
> clustering issues beyond initial configuration and setup.
> 
> Consider the following use case:
> 
> There are two proxmox servers, pm1 and pm2.  Pm1 is runs some important
> production services (db, web server) whose availability must not be
> interrupted.  However, pm1 needs some hardware fixes.  In order to
> maintain service availability, a cluster is created by buying a new
> machine, pm2, to be a child node.  pm2 is empty, so it can be used to
> create a cluster with no problems.  After the cluster is setup, the
> important VMs are live-migrated from pm1 to pm2.  Pm1 is then taken
> offline for repairs, and the import servers continue running
> uninterrupted.  Management and customers are happy.
> 
> What is the best way to manage pm2 while pm1 is offline?  For example,
> if a major hardware problem requires the machine to be offline for
> several days.  Should one use `pveca -m` to make pm2 the master
> temporarily and then again to make pm1 the master once things are back
> to normal?

I suggest you manage the VM´s on the slave on the console:

For OpenVZ: with 'vzctl'
For KVM: with 'qm'

For syntax, see 'man vzctl' and 'man qm'

> 
> If one has a multi-node cluster (3 or more) does running `pveca -m` on
> one node communicate to all other children that it is the new master?
> If not, what is an effective means of getting all of the children to
> recognize the new master?

Just tell all nodes to synchronize from the new master vie pveca.

> 
> Let's say that there is a cluster of 4 machines used by an organization.
>  The organization decides to open a second office and wants to host two
> additional machines at the second location.  Are there any problems with
> extending a cluster in such a way?  It seems like it would be an
> effective means for an IT manager at location 1 to manage the entire
> organization's servers in one place.  The concern here would be if
> something happens to the network connection between the two locations,
> would local staff at location 2 be able to directly manage their proxmox
> instances temporarily through the child web consoles without causing
> problems?

A cluster over WAN is not a good idea, just think of sync. of the ISO files and templates.
I recommend not to cluster the new office to the existing one.

> 
> I look forward to hearing how people have handled these or similar
> situations.  Please feel free to expand to other scenarios, too.

Yes, I am also interested how other use Proxmox VE.
Br, martin


> 
> Many thanks!
> Theron
> 
> --
> 
> Theron Trout
> Principal, Mellonway LLC
> 
> 800-614-MWAY (6929)
> 301-358-5050
> www.mellonway.com
> 
> Efficiency and Results through Expertise. (TM)
> 
> 
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