On Jul 18, 2011, at 11:16 AM, Derek J. Balling wrote:

> Has anyone here done an ESX->XenServer migration before? Tips? Tricks? 
> Gotchas? Tools that you used that you said "Holy crap that made everything 
> easy!"?

I've done a physical -> XenServer 5.6 migration for a number of hosts, and from 
the guest OS's standpoint a migration from VMware is effectively the same as 
one from physical.  The only difference is that you'd need to disable or remove 
VMware Tools.

The biggest gotcha is that XenServer wants Linux guests to be paravirtualized, 
which means that you have to prepare a compatible kernel prior to the 
migration.  Depending on your Linux distributions, this may already be in place 
or may just be a quick package install away.

Also be aware that XenServer is quite sensitive to your Linux distribution.  If 
the one you're using isn't on their supported list, life is going to be much 
harder than it was under VMware.  You *can* run Linux fully virtualized under 
XenServer like you do now with VMware, but you lose the ability to do basic 
stuff like live migration, as well as most insight into guest performance 
metrics.  This may be different in 6.0, but I haven't had time to play with the 
beta yet.

Otherwise, there's a basic list of guest prep work to be done:
  - Install a Xen friendly kernel (see above)
  - Replace any explicit /dev/sdX naming in fstab (or replace with labels or 
use LVM)
  - Prep a new initrd if necessary
  - Adjust grub.conf and /etc/inittab to ensure they're configured to use Xen's 
xvc0 console

Once you have the guests prepped, there are a lot of options for getting your 
data over to a new XenServer container, ranging from rsync to dd to VMDK -> VHD 
conversion utilities.  Play with all the options and determine which works best 
given your current environment, availability of maintenance windows, and 
destination storage type.

I'm sure some of the commercial P2V/V2V utilities can do this for you on the 
fly, but most tend to favor Windows environments because they typically need 
more help.

Also consider whether it's possible to simply re-deploy new guest VMs under Xen 
and migrate just services and data over.  This is where good Linux "DevOps" 
administration practices and application-level balancing and failover become 
*really* handy.

Good luck, and let us know how your evaluation goes!
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