SBS 2003 --> 2011 migration - mailbox move SLOW performance

I'm running an SBS 2003 to 2011 migration and the "Move Mailbox" step is taking a really, really long time.

More info:
Both servers are VM's on an 2x 4-core IBM x3500 box with 24GB RAM and SAS disks (RAID5).  Both VM's have 4 vCPU's and 4gb/12gb RAM (2003/2011).

There are only 15 mailboxes, though they are huge - 11gb down to 1gb, avg size of 4gb per box.  Total info store size is around 65gb.

I am running this as a test migration, so I have snapshots on both servers (allowing me to roll back if it tanks, fix any errors, then continue) - again, this is not live, and the 2 servers can only see each other in the vSwitch.

Is this normal?  Would an offline defrag on the source server make any difference?  Does this seem like a problem on the source (sbs2003) or dest (sbs2011) server?

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Glen KnightCommented:
This is normal.  It will only move 4 mailboxes at a time by default.  It won't move on to another mailbox until one of the 4 threads becomes available.

You can change this but I wouldn't recommend it.

An offline defrag will make no difference and will just be a waste of time with unnecessary downtime for your users.

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Cliff GaliherCommented:
As demazter says, this is normal. Not only does it only move a few mailboxes at a time, the data transfers of those mailboxes will not be even close to saturating your network. 1 to 2 gigs an hour is fairly common, so don't expect to be seeing network or disk speeds like you with with a file copy or similar activity. There is a lot happening behind teh scenes during a mailbox move.
snowdog_2112Author Commented:
Wow.  60 hours to move 12 mailboxes.

Not an answer I like, but we're not grading on whether we like answers.
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