#CANNOT SIGN IN TO LYNC CHECK TO MAKE SURE YOU ARE ONLINE WINDOWS#
Windows fabric gets automatically installed with Lync Server 2013. I first heard about windows fabric with Server 2008 R2 and ever since it has been mentioned in one form or other with Server 2012, Azure etc though never paid any attention to it, until now. Also you do not have to manually configure any of the above processes (other than enabling a user) and what is responsible for creation of user groups and automatic replication of data between FE servers ? – Windows Fabric. The above mentioned replication of user data between FE servers is the single most reason why presence can survive BE SQL server outages. How do FE servers keep user information ? Databases within the servers. This is the method of load balancing used within the FE servers on a Lync Server 2013 pool. if there are 3 servers in a FE pool, Server 1 might contain primary user group 1 and secondary user group 2, Server 2 might contain primary user group 2 and secondary user group 3 and so on. This means that a user group will be assigned to a primary, secondary and tertiary FE server and that the users’ data that is stored on the primary FE server is replicated to the 2 neighbouring FE servers. Each user group is then replicated to two other FE servers. When a user is enabled for Lync, the user is assigned to a User Group. Have you ever wondered which server does the user reside if we enable a user for Lync on a FE pool that contains 5 servers ? The answer is User Groups. Whenever a Lync Server 2013 FE pool is created, 2 things happen. This and the everything that follows is why hardware requirements for Lync 2013 FE servers spiked.
These changes are written back to the BE database, the process commonly known as Lazy writes. FE servers are now given the responsibility of keeping the presence information and other changes within themselves. This is where the Brick Model architecture of Lync Server 2013 comes into play.
It was just a matter of time that Microsoft realised they need to loosen this FEBE coupling to get more out of Lync server. Lync 2013 FE Architecture and what has changed ? This ‘tight coupling’ with SQL BE server is also the culprit behind quite a lot of bottle necks and limitations. This was the reason why any loss of connectivity to the back-end databases would result in reduced functionality mode with loss of presence, access to any form of scheduled conferences and its data and of course, a big red banner saying “Limited functionality due to outage”. The term that I stumbled across on more than one occasion to put it very lightly was ‘tight coupling’ – because the FE servers were constantly querying SQL back-end database for all sorts of info as mentioned above, primarily the presence status updates. As you might know, Lync Server 2010 FE servers / pool used SQL back-end (BE) database to store users’ Contacts lists, presence information, conferencing data including persistent data about the state of all current conferences, and conference scheduling data whilst FE servers provided core functionality such as Instant Messaging (IM), web conferencing, application sharing etc etc.