Wednesday, May 28, 2008

a couple of notes about Domino clustering

I was talking (yes real talk, not IM -- the horror!) with a fellow Notes developer last night and the subject of my ILUG presentation came up. I gave him a thumbnail sketch of what I'm going to be presenting and he seemed surprised that it was possible, so I wanted to spell it out a little more clearly.
  • Domino clustering happens natively in Domino. There is nothing OS specific to it.

  • Therefore you can cluster Domino servers on different server operating systems together. That's right, Windows/Linux, Linux/AIX, AIX/i50S... Domino doesn't care.

  • You can see this demoed LIVE at ILUG next week. I'm on at 9:00 AM on Thursday.


  1. even a "Notes developer" should know the basic fact that a Domino cluster is nothing OS specific.

  2. And it is actually pretty easy and painless to implement.

    And you don't have to have a 1-to-1 relationship. We have 3 servers clustered, with one server that carries replicas from the two other servers and is used for failover.

  3. Not only can you cluster across different OS's you can also cluster across different versions of Domino! This is not really recommended for mail files, but if you have an app that only uses "version N-1" features, you can cluster it on a version N and a version N-1 server while you were upgrading (or to test the app in version N).
    In fact the better reason to do this is to cluster across different point releases, compare and contrast with "clustering" offered by some other products, where you have to keep the clustered servers at exactly the same OS, fix level, version and patches for it to work.

  4. That's gonna be a great presentation Charles.

    I think I've tried it, but cannot remember the result, but can you cluster between partitions within a partitioned server such as iSeries? And those partitions can be at different Domino releases too.

    Also, you could even go so far as to have a Domino cluster with real hardware on one side running on iSeries and a virtual machine running windows or linux on the other end(a great way to stretch the hardware budget btw). If your laptop has enough cpu and ram, it would be easy to setup a demo of clustering in a VMWare Workstation setup using Linux and Windows VM's.

  5. Ulrich: The person I was speaking with, and a few I asked afterwards, were a little surprised that it worked seamlessly with Domino on different server OS's. It wasn't that they thought Domino clustering was OS-dependent, most had just never worked in a mixed environment so they weren't aware.

    Maria/Anonymous: I don't think I'm doing anything ground-breaking, I just haven't ever seen anyone take this on in a presentation before. Maybe it's because it's so trivial, or maybe it's because it's not practical. I'll find out. :-)

    Paul: I've never done it, but I don't see why it wouldn't work. I have a client with an AS/400 they're decommissioning in couple of weeks and I may have a whack at that scenario to see how it works.

  6. Charles,

    The other thing that's overlooked with Domino/Notes clustering is its robustness.

    That comes from the Shared-Nothing architecture. And it's very easy to take for granted.

    Case in point - we recently went through our usual Quarterly Network Outage, when our networks guys get their upgrade/test window in the organisation. Almost everything uses clustering across multiple physical sites, for disaster recovery, so this means everyone has to do a lot of coordination around this kind of event.

    Teams looking after systems using certain OS-based clustering technologies were up at 07:00 on a Sunday to power down their clusters in an orderly fashion. Then they had to phone in to confirm that they were all down and the work could go ahead.

    Me? I stayed very quiet in the meetings about what we'd do in our team. On the Sunday, I rolled towards the on-call Blackberry at 08:55 and phoned in to say we were good to go. Then I went back to my lie-in. :-)

    The loss of a network link between them just wasn't an issue for our clusters. Each box carried on happily, and afterwards anything that had been changed - for instance, by scheduled agents - just got synchronised via replication.

    Gotta love that. Domino Cluster has its plus points and its minus points, but extra hours in bed on a Sunday morning is definitely in the PLUS column! ;-)