Huang Zhen wrote:
Hi,
Some thoughts about our solution for split-site cluster:
1. the split-site cluster includes one or more sites.
2. a site means a set of nodes in one subnet.
No.
A site means a collection of machines in one location connected by local
area networks which can be made reliable for reasonable cost.
3. a subcluster means a set of nodes which can connected each other
in one site.
This is defined on the http://linux-ha.org/ClusterConcepts page. This
page is a bit mathematical in its definitions, but it says what I mean
for it to say. If you have trouble understanding it, please let me know.
4. quorum is required to provide service.
Most - but not all - services require quorum.
5. there are two levels of the quorum, local quorum(or inside a site,
or in one subnet) and global quorum (inter-site, cross site or whole
cluster).
No, there is just quorum. It's for the whole cluster. What you're
calling local quorum isn't quorum. It's just a piece of a voting
mechanism. I wouldn't call it quorum - I think it's too confusing.
6. local quorum means more than half nodes in the site (or by
tie-breaker plugin), in current implementation.
7. calculating local quorum don't need the information of nodes in
other site(s).
The things I put on the web site had several alternatives in them. None
of them use the term "local quorum".
8. global quorum would be decide by 3rd quorum server with the
information of the sites and subclusters.
The quorum server has NO knowledge of sites. You _could_ run this
server for non-split-site clusters and it would work fine.
9. if the subcluster has both the local and global quorums, we say
that it has the quorum.
There is no local quorum.
It sounds like I've succeeded in confusing things :-(
Right now, heartbeat has no idea about sites.
This would have to be added - as would weighting in votes.
You do NOT need any knowledge about sites in the quorum server.
The site concept, and the weighting concept are NOT needed for any
initial implementation.
I guess I need to update the page to make this clearer.
Sorry :-(
--
Alan Robertson <[EMAIL PROTECTED]>
"Openness is the foundation and preservative of friendship... Let me
claim from you at all times your undisguised opinions." - William
Wilberforce
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