Migrating Mailboxes from Exch 2003 to Exch 2010 Painfully Slow

We are migrating from Exch 2003 to Exchange 2010.  Migrating the mailboxes is really slow.
Moving a 3gig mailbox with 60,000 items is taking about 20 hours.  The Exch 2003 side is on physical servers running Win2003 SP2 /Exchange 2003 SP2.  The Exchange 2010 is running on VMWare 4.0 with the latest update in place.  Server 2008 R2 with Exch 2010 SP1.  On the Exch 2008 side we have 3 mailbox servers and 3 CAS/HUB servers.  We have 3 ESX hosts each running 1 mailbox and 1 CAS/HUB server.  Each ESX box has dual 6 core and 96gig of memory.
We are running a DAG with 3 copies - 2 local and 1 to a DR site.  The production net and the replication network both have 2gig cards.  Both the Exch 2003 and 2010 servers are on the same VLAN in the same data center (10 feet away from each other).
I am hearing that this is normal but finding thathard to swallow.  I have users with 30gig mailboxes,,, that could take a week to migrate.  Try telling attornies that...
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jwilmerConnect With a Mentor Author Commented:
I turns out that the problem was with the Exch 2003 Physical Servers.  From the Exch 2003 servers you could copy a 1gig file to 2003 or 2008 with no problem in a few mins.  But if you were 2008 and tried to pull a 1gig file from the Exch 2003 server it would tell you that it was going to take 19 hours.
This is the same thing the 2008 Exch servers were seeing when they were trying to pull or migrate the mailbox from the Exch 2003 servers.  We needed to upgrade the drivers and disable offloading.
AmitIT ArchitectCommented:
Mailbox move normally take long time. Secondly 3GB is not a small mailbox. It is very big. You mentioned, you have a user with 30GB mailbox, that is really big mailbox for Exchange 2003 server. There is no shortcut or tool to make it fast. Use normal mailbox process method. What, I can recommend is to remove all rules from the mailbox and increase the limit for skip the corrupt items. Or You can export data to PST files. Delete data from mailbox and move the empty mailbox. Later merge PST back to mailbox.

Below are the steps for Exchange 2003 - 2010 migration.



Hope this helps
AmitIT ArchitectCommented:
So its not Exchange issue. It looks OS and driver issue.
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jwilmerAuthor Commented:
We ended up working with Microsoft and Dell support for over a day to figure out what the problem was.
Jwilmer, What was the method used to disable offloading on your 2003 server?
jwilmerAuthor Commented:
These were Dell 2950 Servers with Broadcom Cards.  We used the Broadcom Avanced Control Suite 3 utility to changed the settings.  
Disable the following
Receive side scaling and any offloading
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