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

[ml ml]

Hello List,

my aim is to host multiple VMs which are redundant and are high available.
It should also scale well.

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:

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
drbdresource.
- 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.

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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