February 21, 2019 at 3:17 pm
So to help mitigate issues with databases moving to different servers we've added DNS aliases named after the databases and created linked servers using the alias names. Essentially we have a linked server for each database. In addition on each target server there is a login specific to that one database which is used by the linked server so a given linked server only has access to that one database.
When a database moves to another server we just need to update a single DNS entry and everything referencing that will be pointing to the correct place.
We just started to do some conversions and right off the bat had a query that runs in 1 second using the regular hostname linked server, and the same query on the linked server named after the alias ran 23 seconds.
This is discouraging to say the least. I will say on subsequent runs the query was down to about 5 seconds but still thats 5x longer than the other way.
I know the DNS lookup with a cname or alias requires another step. It first gets the hostname from the alias/cname record then goes and gets the A record using the hostname which finally returns the IP.
Does anyone have experience with this sort of setup and able to provide any advice, horror stories, etc...?
thx
February 21, 2019 at 6:13 pm
are you using fully qualified names for the DNS? like myServer.AlphaTangoWhiskey.com, or just the name that has to be resolved, like myServer?
can you test and see if it makes a difference?
Lowell
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