Another Max Memory Question

  • We're planning to install a named instance of SQL 2008 R2 on a server that already has a default instance. Naturally we'll have to reduce the Max memory setting on the default instance to prevent the two instances and OS from wrestling over memory. The server has 32GB of RAM and the default instance Max memory setting is currenly 27GB.

    The total size of all databases on the named instance will be less than 3GB. Is there any additional benefit to setting the max memory to much more then the size of the databases? I'd prefer to give the named instance the minimum amount it needs and the default instance as much as possible because the default instance hosts about 100GB of data for mutliple applications.

  • Based on the load you have mentioned here.yes i think below ratio can work.

    OS - 4 GB

    Named- 4/6 GB

    Default -- 22/24 GB

    BUt keep the memory utilization on your RADAR for few weeks.

    -------Bhuvnesh----------
    I work only to learn Sql Server...though my company pays me for getting their stuff done;-)

  • be aware that the sql memory options are for buffer cache and not the other various memory pools. I generally never use lock pages in memory as this allows you to see how memory is actually being utilised. Note that Tempdb may use as much memory or greater than your database(s)

    As with any such scenario you have to monitor and trend to best tune the resources to the demands of the server. I'm assuming this is all x64 so watch your other memory pools.

    My advice - take a estimate at what you think is fair - then monitor ( record to a table ) and adjust to suit. Taking pot luck might not be the best choice!

    Although I have no affiliation to SQL Diagnostic Manager I'd suggest this as a useful tool to assist.

    [font="Comic Sans MS"]The GrumpyOldDBA[/font]
    www.grumpyolddba.co.uk
    http://sqlblogcasts.com/blogs/grumpyolddba/

  • One thing you can do is to give the new instance an optimistic amount of memory (more than it can use) and then monitor to see how much it actually does use for a while and then adjust your memory settings to a final value.


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