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mochacoffee
03-Aug-2015, 11:01
I am new to SUSE SLES HA
I realize there are several ways to implement fencing.

I am confuse with sbd fencing and STONITH.
I saw that if we implement sbd, we need to create a STONITH as well.

Can I implement STONITH without sbd? without a shared disk.

How good is STONITH fencing?

Given the many types of fencing methods, which one should I choose? How do I make the decision?

Please advise.

Thank you!!!!!

jmozdzen
03-Aug-2015, 11:35
Hi mochacoffee,

I am new to SUSE SLES HA
I realize there are several ways to implement fencing.

I am confuse with sbd fencing and STONITH.
I saw that if we implement sbd, we need to create a STONITH as well.

Can I implement STONITH without sbd? without a shared disk.

How good is STONITH fencing?

Given the many types of fencing methods, which one should I choose? How do I make the decision?

Please advise.

Thank you!!!!!

STONITH is the general fencing technology. It needs a gun, i.e. sbd. So you configure STONITHing in the cluster and tell it which actual mechanisms to use for specific nodes.

I had tried sbd, but it does require reliable disk performance, which did not work out well in my test bed: When the going got rough, all disks were extremely busy, but overall the cluster would have survived. SBD monitoring nevertheless timed out and hence the cluster node(s) were rebooted.

Personally, I do prefer power-based mechanisms, i.e. using SNMP-based PDUs. In case of blade servers, where you'd kill all blades if you cut the power, using IPMI has worked nicely for me.

Regards,
Jens

ab
03-Aug-2015, 11:56
The SLES High Availability Extension (HAE) documentation may answer your
questions better than I can:
https://www.suse.com/documentation/sle_ha/book_sleha/data/sec_ha_storage_protect_fencing.html

In summary, SBD is one way of implementing STONITH, but other ways include
some kind of hardware device that is dedicated to this task. I've never
had to set one of those up, and SBD is available with the HAE solution and
seems to work just fine as long as you follow the rules properly for
setting it up. The biggest rule broken is around number of nodes, which
SHOULD be at least three (3), though many clusters only have two nodes,
and of course requires reliable shared devices for the SBD itself.

--
Good luck.

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David Gersic
03-Aug-2015, 14:30
On Mon, 03 Aug 2015 10:04:01 +0000, mochacoffee wrote:

> I am new to SUSE SLES HA
> I realize there are several ways to implement fencing.

Yes. What hardware are you doing this with? What are your options?


> I am confuse with sbd fencing and STONITH. I saw that if we implement
> sbd, we need to create a STONITH as well.

SBD is another type of STONITH. It's a second way for the cluster to
resolve who is up, who is down, and who needs to be killed to ensure
cluster health, in the event that the nodes cannot communicate via the
network.


> Can I implement STONITH without sbd? without a shared disk.

You can do STONITH without SBD. You can't do SBD without a shared disk.


> How good is STONITH fencing?

Very good.


> Given the many types of fencing methods, which one should I choose? How
> do I make the decision?

What do you have available? If you have something like an ILO that can be
used to remotely down the server, that would work. Or a smart power strip
or UPS that can be told to turn off the server. Basically, you want a
hardware device on nodeX that nodeY can use to turn nodeX off.


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Knowledge Partner http://forums.suse.com

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