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Re: [Linux-cluster] redhat cluster running on debian 6.



On 10/16/2011 07:21 AM, Joey L wrote:
> Digimer - thanks for you input - you saved me a ton of time!!!
> I did look at your tutorial -- great stuff BTW.

Thank you. :)

> I thought fencing was an option because I setup RH cluster about 5
> years ago and I thought I did not do it then..and further in the RHEL
> Cluster Administrator had points that it was optional -can not find
> the url right now. but have pdf and it says:

Maybe in very old versions, but not under EL5 or EL6. Like I said,
RGManager uses DLM and DLM blocks on fence and fence triggers as soon as
a node goes quiet, regardless of if there is a fence device or not.

> "If a cluster node is configured to be fenced by an integrated fence
> device, disable ACPI Soft-Off for
> that node. Disabling ACPI Soft-Off allows an integrated fence device
> to turn off a node immediately
> and completely rather than attempting a clean shutdown (for example,
> shutdown -h now).
> Otherwise, if ACPI Soft-Off is enabled, an integrated fence device can
> take four or more seconds to
> turn off a node (refer to note that follows). In addition, if ACPI
> Soft-Off is enabled and a node panics
> or freezes during shutdown, an integrated fence device may not be able
> to turn off the node. Under
> those circumstances, fencing is delayed or unsuccessful. Consequently,
> when a node is fenced
> with an integrated fence device and ACPI Soft-Off is enabled, a
> cluster recovers slowly or requires
> administrative intervention to recover "

This helps speed up recovery. However, I prefer to leave it on an accept
the 4 seconds delta because I find ACPI soft-off is very handy. In the
end though, the decision depends on your needs.

> But not looking to argue this point at all - i remember that when i
> did set it up it was indeed more stable like you state.
> My Memory is getting old :)

Fencing <3

> About pacemaker --
> Do I need fencing hardware as well ??

Short answer; Yes.

Long answer, you can disable stonith. However, that is always a
tremendous risk because you set yourself up for a bad day if the cluster
is allowed to reconfigure around a blocked node that eventually
unblocks. I *strongly* advice against it. Strictly speaking though; No.

> I just got 2 servers and a regular switch - i think it netgear.
> Like I said earlier - just want the 2 boxes to back up each other.

What you want doesn't really preclude the need to build a proper cluster. :)

> I have mysql, apache, asterisk, dns and nfs client running on them -
> can i do anything with pacemaker ??

Pacemaker and Red Hat cluster will both do this just fine.

> I should mention that I am using software raid but will probably need
> to change to hardware raid in near future.

The cluster doesn't care.

> I would like to use the mysql replication feature -- if possible.

This is a well tested and used configuration. You should have no trouble
getting help.

> thanks for your insight and help.
> 
> mjh

My pleasure. :)

-- 
Digimer
E-Mail:              digimer alteeve com
Freenode handle:     digimer
Papers and Projects: http://alteeve.com
Node Assassin:       http://nodeassassin.org
"At what point did we forget that the Space Shuttle was, essentially,
a program that strapped human beings to an explosion and tried to stab
through the sky with fire and math?"


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