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Mapped Drive vs UNC Performance Differences?

Posted on 2006-10-23
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Is there any performance benefit to using Mapped Drives vs UNC paths?

I'm looking to see if there is less network or resource overhead to using a mapped drive in Windows vs a UNC path that may re-authenticate between calls.

Any documentation to back this up?
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Question by:brandonkirsch
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by:megs28
ID: 17792106
I'm not overly sure as to what you mean when you say UNC vs. mapped drives.  I take it you mean typing '\\server\share' from a run prompt vs. mapping a drive.  With that in mind, I would think that the mapped drive would cause more traffic due to the fact Windows will "check" to see if the connection still exists when you even do simple things such as browse My Computer.  This in turn would cause more load for the OS as well (some people seriously wonder why it takes 2 minutes to open My Computer when they have 20 mapped drives that are rarely accessed).  This amount of traffic shouldn't cause a noticable slow down, and if it is, you need to sit down and examine your infrastructure very closley.

By the way....UNC = \\server\share.  You can map a drive by that, or substitute the server's IP address instead.  And if this is what concerns you and slows your network down...again, you need to examine your infrastructure.
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by:usacadena
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using the static ip address should be the fastest \\10.1.#.#
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by:brandonkirsch
ID: 17795426
I know what a UNC is.  I get what you're saying about opening "My Computer" and all but I'm looking for concrete facts (that is a link to documentation) to base our decision on.

We're making thousands of queries across SMB shares so every millisecond counts.  

Changing to an IP address for \\10.10.* wouldn't make a difference since DNS lookups are cached anyways after the first call.

Does anyone have a link to documentation on the overhead involved with using UNC paths vs Mapping a drive letter?
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usacadena earned 125 total points
ID: 17796226
"Mapped drives show better read performance than UNC paths at request sizes of 64KB and above. Where our mapped drive ran at near disk-speed with large requests, UNC reads dropped to the one and two MB per second range. As the request size increased, the throughput decreased. Interestingly, mapped drives showed good performance at large request sizes, however additional depth caused throughput to decrease. Overall, a depth of two seemed to be the optimum value for both UNC and mapped drives, reading and writing. For good performance, drives should be mapped rather than accessed using their UNC paths."

Ref:

http://research.microsoft.com/BARC/Sequential_IO/Win2K_IO_MSTR_2000_55.doc
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