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waskelton4
Starting Member
12 Posts |
 Posted - 2007-03-02 : 11:06:58
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Hello All,two questions really..1. Does automatic failover in a HA implementation of DB mirroring have to be done by the client software or can it be set in motion by the sql servers alone? we have various dbs that have client programs of various types. (php, asp, 3rd party app...)2. we have 3 servers for this setup but two need to be holding primary databases. like so.. Is this a good idea?many thanks.WillBAD SPELLERS OF THE WORLD UNTIE!! |
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snSQL
Master Smack Fu Yak Hacker
1837 Posts |
Posted - 2007-03-02 : 18:03:51
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| Failover with mirroring is really done by both the servers and the clients.The servers do the failover, so if a primary goes down, the witness and the secondary decide together to initiate automatiic failover and the secondary becomes the primary automatically without any clients doing anything. The clients will keep trying to connect to the primary server. When the connection to the primary fails on the client, then the client will automatically try to connect to the secondary. This automatic switch on the client requires that the client be using the new SQL Server Native client driver, otherwise you'd have to code the client application to try the secondary when the primary fails. The new SQL Native client supports specifying the failover server in the connection string, but the client also receives the name of the failover server from the primary when it connects successfully to the primary.Your server setup looks good. Note that one alternative would be to use one of the three for a witness server only. The way you have it is good because if one primary fails, then you still have both databases available and being hosted by different servers so performance will be good. You'll lose that if you use a dedicated witness server, but because clients will never connect to it you don't have to pay for a license for it. |
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Automatic Failover with DB Mirroring