[Users] Will this two node concept scale and work?

[Dafna Ron]

see in line


On 02/05/2014 10:45 AM, ml ml wrote:
> Hello List,
>
> my aim is to host multiple VMs which are redundant and are high 
> available. It should also scale well.

I'm assuming you are talking about HA cluster since redundancy vm and HA 
vms are a contradiction :)
>
> I think usually people just buy a fat iSCSI Storage and attach this. 
> In my case it should scale well from very small nodes to big ones.
> Therefore an iSCSI Target will bring a lot of overhead (10GBit Links 
> and two Paths, and really i should have a 2nd Hot Standby SAN, too). 
> This makes scalability very hard.
>
> This post is also not meant to be a iscsi discussion.
>
> Since oVirt does not support DRBD out of the box i came up with my own 
> concept:

check out posix storage domain.
If it supports gluster you might be able to use it for DRBD.

>
> http://oi62.tinypic.com/2550xg5.jpg
>
> As far as i can tell i have the following advantages:
> --------------------------------------------------------------------
> - i can start with two simple cheap nodes
> - i could add more disks to my nodes. Maybe even a SSD as a dedicated 
> drbd resource.
> - i can connect the two nodes directly to each other with bonding or 
> infiniband. i dont need a switch or something between it.
>
> Downside:
> ---------------
> - i always need two nodes (as a couple)
>
> Will this setup work for me. So far i think i will be quite happy with it.
> Since the DRBD Resources are shared in dual primary mode i am not sure 
> if ovirt can handle it. It is not allowed to write to a vm disk at the 
> same time.

not true that you cannot write to the same vm disk at the same time - 
you have a shared disk option

>
> The Concept of Linbit 
> (http://www.linbit.com/en/company/news/333-high-available-virtualization-at-a-most-reasonable-price) 
> seems to much of an overhead with the iSCSI Layer and pacemaker setup. 
> Its just too much for such a simple task.
>
> Please tell me that this concept is great and will work and scale well.
> Otherwise i am also thankful for any hints or critical ideas.
>
>
> Thanks a lot,
> Mario
>
>
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-- 
Dafna Ron