Migration from Physical 32-bit OS to Virtual 64-bit OS

[soxfan]

We are in the planning stages of a migration of our Zimbra server from a physical server running under CentOS 4 32-bit to a VMware ESX 4.0 virtual machine which will be running under CentOS 5 64-bit. We are currently running Zimbra Version 6.0.5 FOSS edition.

I'm planning on using the info found in the wiki guide Network Edition: Moving from 32-bit to 64-bit Server to do the migration. Even though the wiki page specifically mentions the Network Edition my understanding is that the procedures will work for the FOSS Edition as well. I've also found a lot of good information in the forums regarding similar migrations.

However, there are a couple of things that I'd like to get some input on.

1) After reading the wiki guide my biggest concern is the length of downtime we will have during the migration process. With 250+ GB of data no matter what process I use to move the data it is going to take quite some time. I'm wondering if there is any way to "stage" the data ahead of time and then use something like rsync to refresh the data when we are ready to do the actual migration.

2) We are right now in the process of upgrading our VMware environment from version 3.5 to version 4.0. We haven't gotten into the nuts and bolts of version 4 yet, but my understanding is that there is new functionality with paravirtualized drivers for storage and networking. Does anyone know if a Zimbra installation can benefit from these new drivers?

If anyone has any thoughts, ideas, or experiences related to these two topics, or would like to share any other info on similar migrations it would be greatly appreciated.

Thanks,
John