Comments on: An underrated cluster admin’s companion: dopd http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/ Linux, DRBD, and other stuff of interest Fri, 21 Nov 2008 09:46:07 +0000 http://wordpress.org/?v=MU hourly 1 By: Florian Haas http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1375 Florian Haas Wed, 02 Jan 2008 17:13:58 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1375 Block-level synchronous replication over a 250kbps link? Good luck. But don't come complaining if your performance goes down the tubes. :-) Block-level synchronous replication over a 250kbps link? Good luck. But don’t come complaining if your performance goes down the tubes. :-)

]]> By: Edward Kantin http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1373 Edward Kantin Wed, 02 Jan 2008 13:12:38 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1373 I know this isn't the "forum" but can you explain why it wouldn't make sense to use it over a DSL link? I'll have at least 250Kbits available for DRBD replication. I know this isn’t the “forum” but can you explain why it wouldn’t make sense to use it over a DSL link? I’ll have at least 250Kbits available for DRBD replication.

]]> By: Florian Haas http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1371 Florian Haas Wed, 02 Jan 2008 08:39:59 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1371 Edward, dopd is unlikely to help you in your scenario, as it would usually make little sense to use DRBD over a DSL connection. Except perhaps with protocol A and extremely low write load. But you're probably better off with csync2. Edward,

dopd is unlikely to help you in your scenario, as it would usually make little sense to use DRBD over a DSL connection. Except perhaps with protocol A and extremely low write load. But you’re probably better off with csync2.

]]> By: Edward Kantin http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1369 Edward Kantin Wed, 02 Jan 2008 01:48:10 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1369 I'm looking at a setup where the only available communication between nodes would be a dsl connection. I'd like to have a dial on demand ppp connection available for situations where the replication link is broken, I can protect the data against split brain issues. Would dopd help me there? I’m looking at a setup where the only available communication between nodes would be a dsl connection. I’d like to have a dial on demand ppp connection available for situations where the replication link is broken, I can protect the data against split brain issues. Would dopd help me there?

]]> By: Rois http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1183 Rois Fri, 07 Dec 2007 17:27:02 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1183 OK . . . Back tracking a little here. Still would like to know where I can get some dopd doc's but appearantly "drbdadm outdate all" doesn't work unless the dopd nodes are disconnected. I tried disconnecting and it worked. Upon closer inspection of the dopd syslog error it appears that it's looking for drbdadm in /sbin and my distro has it in /usr/sbin. I tried copying and ln -s drbdadm, drbdsetup and drbdmeta to /sbin but neither option works and now the log shows unknown exit code from /sbin/drbdadm outdate all: 126 instead of unknown exit code from /sbin/drbdadm outdate all: 127 Any clues to where the path problem is? I'll put this on the forum as well. Thanx OK . . . Back tracking a little here. Still would like to know where I can get some dopd doc’s but appearantly “drbdadm outdate all” doesn’t work unless the dopd nodes are disconnected. I tried disconnecting and it worked.

Upon closer inspection of the dopd syslog error it appears that it’s looking for drbdadm in /sbin and my distro has it in /usr/sbin. I tried copying and ln -s drbdadm, drbdsetup and drbdmeta to /sbin but neither option works and now the log shows
unknown exit code from /sbin/drbdadm outdate all: 126
instead of
unknown exit code from /sbin/drbdadm outdate all: 127

Any clues to where the path problem is?
I’ll put this on the forum as well.
Thanx

]]> By: Rois http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1182 Rois Fri, 07 Dec 2007 16:31:58 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1182 Florian, Can you tell me how to get more debugging info? dopd does not appear to be working and I believe I've tracked it down to drbdsetup NOT being able to outdate the local resources. I've tried running the command manually on the peer and it does nothing. I know outdate works somehow because "fencing resource-only;" is doing it. Here is my basic understanding of what dopd is suppose to do: Primary sends a message to the secondary to outdate itself. The secondary is suppose to run the command drbdadm outdate all. If I run "drbdadm -d outdate all" it shows me that what is being run is: drbdsetup /dev/drbd0 outdate drbdmeta /dev/drbd0 v08 /dev/vg0/home internal outdate Running drbdsetup on the secondary does not outdate the resources, does not return any messages and does not log anything to syslog. Running drbdmeta returns "Device '/dev/drbd0' is configured!" but does not outdate the resource and does not log anything. Is there any other documentation on dopd or drbd that might help me figure out what my problem is. Thx Florian,
Can you tell me how to get more debugging info? dopd does not appear to be working and I believe I’ve tracked it down to drbdsetup NOT being able to outdate the local resources. I’ve tried running the command manually on the peer and it does nothing. I know outdate works somehow because “fencing resource-only;” is doing it.

Here is my basic understanding of what dopd is suppose to do:
Primary sends a message to the secondary to outdate itself. The secondary is suppose to run the command
drbdadm outdate all.

If I run “drbdadm -d outdate all” it shows me that what is being run is:
drbdsetup /dev/drbd0 outdate
drbdmeta /dev/drbd0 v08 /dev/vg0/home internal outdate

Running drbdsetup on the secondary does not outdate the resources, does not return any messages and does not log anything to syslog.

Running drbdmeta returns “Device ‘/dev/drbd0′ is configured!” but does not outdate the resource and does not log anything.

Is there any other documentation on dopd or drbd that might help me figure out what my problem is.
Thx

]]> By: Florian Haas http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1153 Florian Haas Fri, 30 Nov 2007 20:42:07 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1153 Rois, your assumption is incorrect. A highly available system that only runs when both nodes are up wouldn't be highly available. dopd just keeps you from failing over to a node that happens to have bad data. If you just want to disable automatic failback -- and it seems like that's what you're trying to do -- just set auto_failback to off (Heartbeat version 1 and version 2 in non-CRM mode), or set a high default resource stickiness (Heartbeat 2 with CRM). Cheers, Florian Rois,

your assumption is incorrect. A highly available system that only runs when both nodes are up wouldn’t be highly available. dopd just keeps you from failing over to a node that happens to have bad data.

If you just want to disable automatic failback — and it seems like that’s what you’re trying to do — just set auto_failback to off (Heartbeat version 1 and version 2 in non-CRM mode), or set a high default resource stickiness (Heartbeat 2 with CRM).

Cheers,
Florian

]]> By: Rois http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1152 Rois Fri, 30 Nov 2007 20:20:58 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-1152 This appears to have the effect of keeping ha from rolling over to a node with no connections problems. Which means that the system only works if both nodes are working, correct? I'm trying to figure out how to keep an ha failed node from becoming primary again (once it has been rolled to secondary by ha) without user intervention. Can I use dopd for that somehow? I submitted this question to the user list but this is the first time I've heard about dopd. Thoughts?? Rois This appears to have the effect of keeping ha from rolling over to a node with no connections problems. Which means that the system only works if both nodes are working, correct? I’m trying to figure out how to keep an ha failed node from becoming primary again (once it has been rolled to secondary by ha) without user intervention. Can I use dopd for that somehow? I submitted this question to the user list but this is the first time I’ve heard about dopd.
Thoughts??
Rois

]]> By: Florian Haas http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-834 Florian Haas Tue, 02 Oct 2007 07:45:25 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-834 Can I ask you to post your issue on the drbd-user mailing list? Please do not forget to give your exact DRBD, Heartbeat and kernel version, and attach your drbd.conf and ha.cf, and relevant portions of your syslog. You may subscribe to the mailing list at http://lists.linbit.com/listinfo/drbd-user Can I ask you to post your issue on the drbd-user mailing list? Please do not forget to give your exact DRBD, Heartbeat and kernel version, and attach your drbd.conf and ha.cf, and relevant portions of your syslog.

You may subscribe to the mailing list at http://lists.linbit.com/listinfo/drbd-user

]]> By: kimseong http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-827 kimseong Mon, 01 Oct 2007 22:37:58 +0000 http://fghaas.wordpress.com/2007/10/01/an-underrated-cluster-admins-companion-dopd/#comment-827 I have just done exactly this 1 or 2 weeks ago, by reading the instruction on a file in the drbd source. I found that sometimes when the link comes up again, the drbd status on 1 side stays Standalone instead of automatically connect and sync. Have to try to do drbdadm connect to make it connects. And, I have 2 resources on the same link on different port, when the outdate happens, it seems to show Outdated on 1 of the resource, but not both in the /proc/drbd file. I am new with drbd, still learning and trying. I have just done exactly this 1 or 2 weeks ago, by reading the instruction on a file in the drbd source.

I found that sometimes when the link comes up again, the drbd status on 1 side stays Standalone instead of automatically connect and sync.
Have to try to do drbdadm connect to make it connects.

And, I have 2 resources on the same link on different port, when the outdate happens, it seems to show Outdated on 1 of the resource, but not both in the /proc/drbd file.

I am new with drbd, still learning and trying.

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