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estimate disk size for system dbs for a 50 GB app db.

  • May 26, 2010 at 5:20 am

    #145149

    Hi there,

    I've been asked to estimate system db disk size for a 50 GB app db that I know nothing about. The app db is not installed anywhere I can look at.

    1). I guess the main variable is tempdb. Is there any way to estimate this or is it entirely dependent on how much the app likes using tempdb?

    2). What is the recommended log size percentage on a 50 GB app db.

    Sorry if these are dumb questions / covered elsewhere. I did look.

    Thank you.

  • May 26, 2010 at 7:09 am

    #1172681

    for me, i use a rule of thumb of 10% of the mdf size as the needed log size, but the correct answer is "it depends".

    If your database is in simple recovery mode and not full, it will usually not expand the log much unless you have a huge transaction.

    full recovery mode requires a regualr backup of full and incremental bacups to keep the log from expanding out of control.

    the log grows depending on the amount of changes to the database(insert/update/delete)

    if the database has no changes, there's nothing in the log, so accordingly there is no need for a large log in the first place...a lookup database of every zip plus 4 database would be like that...zero changes, but accessed a lot for information.

    the other side of the coin is a database which changes a lot...if the log is too small, it will grow as needed unless otherwise restricted; doing regualr log backups is the key there.

    Lowell

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