I think this thread presented some very good information on a complex topic. However, from a design perspective if you are running VoIP then you should have that data flow in the priority queue from the beginning. Though not many folks run jumbo frames, but those that do should be aware of a bug enabling B/W sharing and jumbo frames. Check software release notes. This bug also applies to Blade 3130's. For those that want to peel the onion back a few more layers. I found a blog document "Understanding the Egress QoS logic on the C3750/C3560/C3750E/C3560E platforms" which goes into much greater detail then Shashank presented above.
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