[addendum inline] On 04/08/17 18:35 +0200, Jan Pokorný wrote: > On 03/08/17 20:37 +0530, sharafraz khan wrote: >> I am new to clustering so please ignore if my Question sounds silly, i have >> a requirement were in i need to create cluster for ERP application with >> apache, VIP component,below is the scenario >> >> We have 5 Sites, >> 1. DC >> 2. Site A >> 3. Site B >> 4. Site C >> 5. Site D >> >> Over here we need to configure HA as such that DC would be the primary Node >> hosting application & be accessed from by all the users in each sites, in >> case of Failure of DC Node, Site users should automatically be switched to >> there local ERP server, and not to the Nodes at other sites, so >> communication would be as below >> >> DC < -- > Site A >> DC < -- > Site B >> DC < -- > Site C >> DC < -- > Site D >> >> Now the challenge is >> >> 1. If i create a cluster between say DC < -- > Site A it won't allow me to >> create another cluster on DC with other sites >> >> 2. if i setup all the nodes in single cluster how can i ensure that in case >> of Node Failure or loss of connectivity to DC node from any site, users >> from that sites should be switched to Local ERP node and not to nodes on >> other site. >> >> a urgent response and help would be quite helpful > > From your description, I suppose you are limited to just a single > machine per site/DC (making the overall picture prone to double > fault, first DC goes down, then any of the sites goes down, then > at least the clients of that very site encounter the downtime). > Otherwise I'd suggest looking at booth project that facilitates > inter-cluster (back to your "multi cluster") decisions, extending > upon pacemaker performing the intra-cluster ones. > > Using a single cluster approach, you should certainly be able to > model your fallback scenario, something like: > > - define a group A (VIP, apache, app), infinity-located with DC > - define a different group B with the same content, set up as clone > B_clone being (-infinity)-located with DC > - set up ordering "B_clone starts when A stops", of "Mandatory" kind > > Further tweaks may be needed.
Hmm, actually VIP would not help much here, even if "ip" adapted per host ("#uname") as there're two conflicting principles ("globality" of the network for serving from DC vs. locality when serving from particular sites _in parallel_). Something more sophisticated would likely be needed. -- Poki
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