Hi Nils, Thanks a lot for all the information provided by you, It a great rescue.
ajit On Tue, Oct 27, 2009 at 7:28 PM, Nils Goroll <slink at schokola.de> wrote: > Hi Ajit, > >> But even in the case VxFS cfs, the other node is not allowed to >> mount if the first node has not mounted the filesystem with share >> mount option, so I was just wondering if ufs has any such mechanism. > > Not that I was aware of, no. Again, I agree that such a mechanism could be > helpful to avoid errors in corner cases, but it would add more complexity, > so I think there should a strong reason before an implementation of such a > mechanism was considered. > >>> If the application needs "raw" device access, then, yes, it should >>> cooperate. If it doesn't or when in doubt, you can use the OHAC/Sun >>> Cluster >>> framework to guarantee that the application will only ever run on one >>> node >>> at a time (for instance using Failover_mode HARD as a last resort, see >>> r_properties(5)). >> >> as far as I could understand about the different Failover_mode >> options, it tells what is behavior if any of the methods (prestart, >> start, stop or poststop) ?fail. It does say any thing about the device >> access in fail-over cluster. > > Correct, what I was referring to is that the cluster can guarantee that the > application will only ever run once by making sure that it gets stopped > somehow: Either by a successful stop routine (and PMF reporting all > processes to have exited) or, as a last resort, by panicking the node. So > this mechanism should implicitly solve issues with potential concurrent > access. > >> Looks like its a expected behavior that offline devices are accessible >> same as online devices in even fail-over cluster. > > Regarding design questions, I would rather refer you to someone from the > core team, but my understanding is that implementation of global, uniform > access to devices (from all nodes) as been a very early design decision in > Sun Cluster 3 history and has been promoted as an important feature: > > http://docs.sun.com/app/docs/doc/820-2554/cacheafd?l=en&a=view > > And, yes, the behavior you are seeing is exactly what is to be expected in > Sun Cluster. > > Maybe your question is related to the fact that OHAC/Sun Cluster does not > have a notion of a Scalable or HA Cluster, but those notions apply to > resource groups. > > Nils >
