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Migrating a linux server using rsync
The problem
We are migrating from a XenServer 6.0 infrastructure to a Hyper-V 2012R2 based one. We already migrated most VMs (Linux and Windows), so only a few remains, but they are the ones with the biggest disks. One of those is a proxy/mail server, based on a customized Gentoo distro. We usually can afford to turn off our servers on weekends, so we chose to do so, and export the various VHDs to a NAS and import them to the new infrastructure. For Linux VMs, migrating from XenServer to Hyper-V means also fixing the device names (xvd* to sd*) and the boot loader, and generating a new initrd. This is a really slow and painful process, since it involves a long downtime and a double file copy, and the NAS is not so fast (it’s a entry level QNAP NAS, ArmV6 based). Moreover, the mail server has two disks, a 16GB and a 300GB disk, ~40% full, so it would take a very long time to export and import. Having a long downtime for the mail server isn’t very nice, since incoming e-mails could be rejected.