How much allocated space for log/data is too much? (SQL Server 2008)

This is a somewhat unusual question...

Is there such a thing as too big of an allocation for data and log files for SQL Server?

Please note, that I am NOT talking about running out of space.

Let's assum开发者_高级运维e for the moment that there is infinite storage, but limited I/O throughput. Does the size of the unfilled portions of data and log files the server is accessing matter for performance? For example, if I have a log file for tempdb that only ever fills up to ~5mb, but have a terabyte allocated to it, would the I/O operations accessing this log complete faster if I reduced allocation to 10mb?

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No, allocated size will not affect perfomance. Perfomance is affected only on file growth.