[DRBD-user] Where to find review of DRBD vs Corosync

Digimer lists at alteeve.ca
Mon Aug 20 15:47:24 CEST 2012

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Happy to help. And ya, the cluster folks were just as helpful when I was
starting out. It's a pretty awesome group. :)


On 08/20/2012 03:57 AM, Bruce Wolfe, M.S.W., CIO wrote:
> TOTALLY!!! Woo-Hoo!  You're the best, Digimer. I appreciate (all of)
> your constant patience with us newbies. This is one of the few open
> source communities that is truly inviting and accepting to help promote
> the use of excellent product and support.
> Kudos to all!!
> Bruce M. Wolfe, M.S.W., CIO
>          24 Belvedere St.
>     San Rafael, CA 94901  
> 415/456.5692  (Main Office)
> 415/257.2493  (Direct)
> 415/456.0491  (Fax)
>            KI6BSL  (HAM)
> "Most of the change we think we see in life is due to truths being in
> and out of favor." - Robert Frost
> ------------------------------------------------------------------------
>     On 08/16/2012 07:38 PM, Bruce Wolfe, M.S.W., CIO wrote:
>     > Thanks, Digimer, and greetings again.
>     >
>     > The configuration is:
>     > Failover of primary to secondary.
>     > Two nodes: one primary, one secondary in, as you say, a RAID 1
>     > configuration.
>     >
>     > So, all three get used? In our current configuration, we are only
>     using
>     > DRBD and Heartbeat.
>     To get automatic recovery after failure, yes, you need all three.
>     DRBD simply replicates raw data. That's it, nothing more. Promoting a
>     secondary node to primary requires external actions, be it by the user
>     or via another program.
>     Heartbeat is deprecated and has no future. Anyone using it should be
>     making near-term plans to get off of it. So let's take the right off the
>     table.
>     Corosync is a stand alone tool that handles cluster membership and
>     message passing. It doesn't care what other programs do or how they use
>     it's message passing capabilities. It is merely a communications tool.
>     Specifically; It decided who can send and receive messages amoungst a
>     group of machines. In our case, we want this so that pacemaker can
>     coordinate actions.
>     Pacemaker is a cluster resource manager. That is, it reacts to changes
>     in cluster membership and, based on defined policies, decides to stop,
>     start, migrate or otherwise act on services. It doesn't care *how*
>     machines in the cluster come and go, only that they do.
>     So in your use case, you would setup DRBD to replicate data. Next, you
>     would configure corosync to say "these two nodes are members of cluster
>     X". Then you tell Pacemaker; "When both nodes are available, make node
>     1's DRBD the primary and make node 2 secondary. However, if not 1 dies,
>     promote node 2 to primary. When node 1 returns, demote node 2 and
>     promote noed 1."
>     Make sense?
>     -- 
>     Digimer
>     Papers and Projects: https://alteeve.com

Papers and Projects: https://alteeve.ca

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