Mandatory and advisory ordering in Pacemaker

Posted on Thu 22 March 2012 in hints-and-kinks • Tagged with Pacemaker

Ever wonder what's the difference between order <name> inf: <first-resource> <second-resource> and a score of something other than inf? We'll explain.

If you specify an order constraint score of INFINITY (inf or the keyword mandatory in crm shell syntax), then the order constraint is considered mandatory. If you specify 0 …


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Managing cron jobs with Pacemaker

Posted on Mon 19 March 2012 in hints-and-kinks • Tagged with Pacemaker

It's not uncommon in Pacemaker clusters to run specific cron jobs only on a node that currently runs a particular resource. The ocf:heartbeat:symlink resource agent can be exceptionally helpful in this situation. Here's how to use it.

Suppose you've got a cron job for Postfix whose definition normally …


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What's a Totem "Retransmit List" all about in Corosync?

Posted on Thu 15 March 2012 in hints-and-kinks • Tagged with Corosync

Occasionally, you may see errors similar to this in your system logs:

corosync [TOTEM ] Retransmit List: e4 e5 e7 e8 ea eb ed ee

Here's what causes them, and what you can do to fix the issue.

Corosync, more specifically its Totem protocol implementation, defines a maximum number of cluster …


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Finding out which OSDs currently store a specific RADOS object

Posted on Fri 09 March 2012 in hints-and-kinks • Tagged with Ceph

Ever wanted to know just which of your OSDs a RADOS object is currently stored in? Here's how.

Suppose you've got an RBD device, named test. Then you can use the rbd info command to display which name prefix is used by the RADOS objects that make up the RBD …


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Solve a DRBD split-brain in 4 steps

Posted on Tue 06 March 2012 in hints-and-kinks • Tagged with DRBD

Whenever a DRBD setup runs into a situation where the replication network is disconnected and fencing policy is set to dont-care (default), there is the potential risk of a split-brain. Even with resource level fencing or STONITH setup, there are corner cases that will end up in a split-brain.

When …


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