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  1. #1
    Join Date
    Jan 2007
    Posts
    56

    Unanswered: Puzzled by database slow down after move to Amazon instance

    Hello,

    We have recently moved a database to Amazon EC2 instance. We chose the server with identical configurations. The performance on the new server is awful. After initial analysis I realized that the old one used much more memory through AWE enable option, and so I reset memory on the new server the same way. However, it does not seem to have helped the problem.

    The only idea I have is to rebuild indexes. The only problem is that db size is pretty big (~ 80 GB) so it might take a while. So before doing that I wanted to get some opinions as to whether I am on the right track or there is something else to check.

    Thank you!

  2. #2
    Join Date
    Jun 2003
    Location
    Toronto, Canada
    Posts
    5,516
    Provided Answers: 1
    It's possible that the SQL Server performance setting got reset during the move. Go to the Advanced page of SQL Server properties and in the Performance drop-down list, instead of "Awful" select "Same as before" or "Better than ever".

    Seriously though, you should start with defining "performance" and "awful". You did not mention your application has moved too, so one can assume it still resides outside the Amazon cloud. In that case network latency would be my first suspect, not SQL Server.
    ---
    "It does not work" is not a valid problem statement.

  3. #3
    Join Date
    Jan 2007
    Posts
    56
    Hello,

    We have a table called 'Articles' which has a clustered index on the ArticleID field. When I run 'SELECT MAX(ArticleID) FROM Articles WITH(NOLOCK)', I get result immediately on old server, whereas on the new server the query is running and running ... Similar simple queries are performing the same way. This is what I meant by an awful performnace.

    As for the applications, we did not test them yet. I simply remotely connected to the machine, opened Query Analyzer and ran a query.

    I found out that there is a difference the machines actually. The old one had 8 CPUs and the new one has only 4. Could this be causing such a slow down?

    Thank you!

  4. #4
    Join Date
    Jun 2003
    Location
    Toronto, Canada
    Posts
    5,516
    Provided Answers: 1
    Quote Originally Posted by sql_er View Post
    The old one had 8 CPUs and the new one has only 4. Could this be causing such a slow down?
    Only if your system is CPU-bound. Take a look at the Windows Performance Monitor counters to see what (if anything) consumes most CPU. At the same time look at the I/O counters.

    Another starting point would be to make sure table stats are up to date and compare the query execution plan on both the old and new server to see if there has been change.
    ---
    "It does not work" is not a valid problem statement.

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