[CentOS] Question about clustering

[SilverTip257]

On Wed, Jun 18, 2014 at 2:46 PM, <m.roth at 5-cent.us> wrote:

> Digimer wrote:
> > On 18/06/14 12:32 PM, Alessandro Baggi wrote:
> >> Ok, fencing is a requirement for a cluster for hardware failure.
> >> I've  another question about this arg, but for software failure.
> >> Supposing to have a cluster of httpd installation on 6 virtualized
> >> hosts, each one on a different server. Suppose also that a guest (named
> >> host6) has a problem and can't start apache. With this scenario, the
> >> ipmi, ups are unnecessary. How to work fencing in this way? How to make
> >> fencing node?
> >>
> > I'm not sure I understand properly... You mean that you have 6 VMs which
> > are nodes in a cluster, or 6 nodes, each hosting a VM you want to make
> HA?
> <snip>
> I'm not clear on what you mean, either. Is this supposed to be a
> load-balancing cluster? If so, and you expect that kind of load, I,
>

My interpretation mirrors Mark's ... sounds like you want to load balance
between the six servers.
If so, you might create a proxy with haproxy [0] [1] that will relegate
connections to each of your six nodes.

[0] http://haproxy.1wt.eu/download/1.4/doc/configuration.txt
[1] http://www.rackspace.com/knowledge_center/article/setting-up-haproxy


> personally, would *never* put a VM on them - I'd want the full resources
> of the o/s brought to bear on that load, and use multiple real hardware
>

Makes sense in the terms of hardware redundancy, but if it's OS level
redundancy then this could fly.  _BUT_ it isn't as ideal as having separate
hardware.  If Alessandro's VMs are clustered between a pair of nodes with
shared/replicated storage, then I'd say it is a realistic scenario.
 Layered redundancy for the win!  (akin to layered security)

Rackspace has haproxy as part of their cloud offerings [2].
Albeit likely resources not on the same single piece of hardware!


> for the other members. Doing this with VMs is only multi-threading the
> load, and adding more, with all the context switches.
>
>      mark
>
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-- 
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Mike
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