We currently have a mixed ESX v3.5 & ESXi 4.0 farm that's at capacity, due to CPU compatability issues I want to build a new farm with new host servers to replace the existing farm (inc. a new vCenter VM). Plan is to use ESXi 5 on the new farm (assuming it gets released in the next week or so). However I'm not entirely sure what my migration options.
I currently have about 4TB of VMs across 6 datastores and can config a temp 1TB datastore to use during the migration process.
I was originally thinking I could format the new datastore as VMFS 5 and have the new ESX 5 see that but then also mask them on the SAN so the new farm can see the old datastores (and not write a new sig when prompted on discovery) - however I'm guessing this will actually cause a conflict as there's no communication between the old and new farms so I/O will clash?
So is my only option to shutdown all the VMs on an existing datastore, disconnect that store from the current farm and reconnect it to the new farm and import the VMs into the new farm, then svmotion the VMs off it to the new temp VMFS 5 store, delete the old store and recreate as a VMFS 5 store and repeat the process for the remaining stores. This obviously involves VM downtime but I can't see any other way (unless having a datastore shared between two separate farms actually works...).
why not upgrade the existing vcenter and create a new cluster for your new hosts. this way you can attach them to both the old and new storage then simple vmotion then svMotion all the machines over to new hosts+storage with no downtime.
this is our plan for migrating out ESX4.1 / Openfiler setup over to ESXi5 / Dell MD SAN later this week when 5 gets released
Yeah that's a decent option and one we'd considered but our current vCenter is all on a single VM and has been upgraded a couple of times already. Keen to build a fresh 3-server vCenter and make sure everything's done the right way from the start rather than worry about issues later. I think we'd have some licence issues to unless we upgraded the v3.5 hosts (which we can't do as I don't have n+1 capacity on the current farm so can't even put a host in maintenance mode at the moment).
Note that ESXi 5 can work without problem with VMFS3.
After you have upgrade all the hosts you can convert VMFS3 to 5 without VM interruptions.