I am glad to see that, as it inches towards standardization in the DMTF, the CMDBf specification is getting more visibility. Forrester’s Glenn O’Donnell recently wrote very positively about it on his blog, presenting it as a key enabler for a federation of MDRs (Management Data Repositories, a term introduced by the CMDBf specification so don’t look for it in ITIL). He argues this is the only way (rather than a single data store) to fulfill the ITIL-defined role of a CMS. Rob England (the IT Skeptic) has also shared his thoughts about CMDBf and they were noticeably less enthusiastic, to say the least. While Glenn calls the specification “profound”, Rob calls it “the most over-hyped vendor marketing smokescreen ever”. There is plenty of room in between them, which is where I sit. As I explained before, it does have real value (as a query language/protocol for system integration) but is nowhere near providing “federation” capabilities.
I am happy to see Glenn approve of CMDBf and I agree with him that accurate specialized MDRs are more useful than a single store that attempts to capture all the relevant data. As Glenn puts it, “pockets of the truth are far superior to unified ambiguity”. But I wasn’t very comfortable with the tone of his article, which seemed to almost encourage the proliferation of these MDRs. Maybe he was just trying to present a clean break with the “one big CMDB” approach and overreached. Or maybe I am just not reading properly.
Because while I agree that the answer is not “one and only one store” I also don’t want to loose the value of having as much unification of the IT model as possible. Both at the data level (i.e. same metamodel/model, consistent retention/roll-up policies…) and the access level (i.e. in the same physical store, with shared access control, accessible using a well-known DSL for data manipulation…). Metamodel transformation and model bridging are costly (in accuracy, maintenance, reliability). If your CMS does more than just support a “model navigation” GUI it may then need to run large queries that go across several portions of your IT model, including multiple different domains (e.g. a compliance rule kicked-off at the app level based on the type of data it manipulates that ends up having to look at the physical location of the servers running the hypervisors for the virtual machines that power the app). Through such global queries you can apply configuration rules, do impact analysis, event correlation, provide context to your transaction tracing, etc. No consolidation means no such queries (or a very limited subset). Considering the current state of federation, there is a lot more that you can do with your CMS if you have a very small number of MDRs rather than a sea of “federated” MDRs. This is why, as Oracle acquires IT management companies, we deliberately integrate their repositories with Enterprise Manager.
[UPDATED 2009/4/8: More, along the same line, from Glenn and his co-author Carlos Casanova available here. And my CMDBf partner-in-crime Van Wiles also responded to Glenn, bringing a BMC perspective.]
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