I have gone through many articles about OAB generation in Exchange 2013 inlcuding some of below mentioned.
http://blogs.technet.com/b/exchange/archive/2012/10/26/oab-in-exchange-server-2013.aspx
http://clintboessen.blogspot.in/2014/03/how-oab-distribution-works-in-exchange.html
But haven't got the answer i needed, my enviroment is a 3 node DAG (2013) multirole
I had issue with OAB download recently, and while troubleshooting i noticed that on each server OAB location
E:\Microsoft\Exchange Server\V15\ClientAccess\OAB\a8954b91-39b9-4922-a4f1-1bda59e42af4
it showed me a different last modified date. and the server which holds the MBX and OAB arbitration mailbox is only has the recent updated files and other 2 nodes have very old files. Hence wondering does this look normal.
Should not all 3 nodes should have the same file update version as when the database is failed over to other node there should not be OAB issue.