[Xen-users] GFS, GNBD, Clustering, DRBD High Availability questions

["Tait Clarridge" <Tait.Clarridge@xxxxxxxxxxxx>]

Hello,

I just wanted to ask if anyone has any experience with Xen and GFS/GNBD 
clustering and/or DRBD high availability setups, any experiences will do.

What I would like to do is setup 2 Xen Servers (8 cores and 64GB memory) with a 
shared storage for failover and migration but would like them both to be able 
to access the storage simultaneously.

I would want to basically connect the two local hardware RAID5 arrays between 
servers using DRBD for VM storage (the VMs are stored in single image files) 
that can be served to both servers using GNBD.

Do I even need to implement GNDB? Could I do a Primary/Primary DRBD GFS?

Each server should be able to see all the VMs and freely migrate between, but I 
was wondering if it is smart to re-import the LVMs from the DRBD disk through 
GNBD and if there are any issues with that. I think I need a little 
clarification as well on DRBD because I came across an article that talked 
about primary/secondary and I was wondering if in the event of a failure, the 
secondary automatically becomes primary and would continue to export GNBD 
normally without any interruption? I've heard about Heartbeat for this but 
again I am unsure of its application in this setup.

This is a little diagram I have to try and explain my above thoughts...


---------------------------                    ---------------------------
|         |Host #1|               |                          |     |Host #2|    
 |
|         ---------               |                          |     ---------    
 |
|                                 |                          |                  
                 |
|       -----------------   |      ________          |  ----------------   |
|     | RAID5       |   |          | DRBD?|          |  |       RAID5      |   |
|       |                   |<======dedicated=1GB=NIC======>|              |   |
|     |  vm storage   |   |             ||           |      |  vm storage  |   |
|     -----------------   |             ||           |  ----------------   |
|                                 |         \/         |                        
         |
|                                 |    ------------    |                        
         |
|       ----------------          |      |   GNBD   |    |      
----------------         |
|       |                  |      |      ------------    |      |               
   |     |
|       |       Dom0       |      |             ||           |  |       Dom0    
   |   |
|       |               <===1GB Network===  =====1GB Network==>            |   |
|       |                  |    |                            |  |               
   |     |
|       ----------------    |                        |  ----------------        
 |
---------------------------                          ---------------------------

Any information would be appreciated, I've read that DRBD is now able to be 
integrated into Xen but I don't think that applies here because we already have 
the virtual machines as image files on an NFS mount.

Thanks in advance.

Tait Clarridge


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