High Availability?

Hi folks, My customer (on MS SQL platform) is asking whether can Navision support High Availability, such as load balancing when one server fails, the other server takes over… Anyone did this before please share your thoughts… Thanks.

“High Availability” (HA) is not load balancing. HA is the concept of having the system “available” with VERY little unplanned downtime. “Load balancing” is the function of balancing the processing load of the application serverS (plural), NOT the database server (singular) so the users response time is somewhat evened out. This is how it works on SAP R/3, not sure how this function works on Navision, but I would presume the same. I think the HA function you are referring to is clustering. BUT…as I understand, when the primary server “fails” you will loose the transaction data that was in process at the time on the failed primary server. w/o clustering you would set up 2 servers with log shipping from the primary to the backup server. What you have to determine is how much data you could afford to loose, which determines how often the log is shipped from the primary to backup server. Last I heard, this is how MS itself is configured for their SAP R/3 installation. There is also “replication” although I have not read enough about it to know it’s capabilities and limitations. Both log shipping and replication will require a manual effort to switch over to the backup server. There are probably other 3rd party solutions out there to minimize down-time from a system crash. As to the front-end, your network people will have to do the server name redirection from the primary to backup server, probably with a change to the DNS table, or rename the backup server to the same name as the primary server. The network guys will have to get involved here. I think you will need to research both MS Clustering and MS SQL Server, if you want to stay with a MS solution. gud luk Gary

cylim for high availability we run “Legato CoStandbyServer” with our Navision database. It works with the C/Side-Database and SQL as well. But there is NO load balancing with this solution - the only purpose is availability. For that we run two fully equipped and from each other independent Database-Servers. On both machines “Legato CoStandbyServer” is installed and the both are connected over a dedicated 1GBit Fiber-Link. There is a permanant mirroring of all data between the two servers on a very low level. Both are visible for our users through one virtual IP-address and one virtual network-name. In fact the database server is always active only on on of the two machines - the second is passive. The user is not aware which sever is currently running. In case of failure or maintainance we switch from the currently active machine to the passive. The switching also can be done automatically. We also run this system for our fileserver and our exchange-server. See http://www.legato.com/products/availability/windows/

Richard Nice to know about the vitural IP and name. I figured something like that existed, but I don’t hang out w the network guys enough. Gary