This article originally appeared on SearchServerVirtualization.com.
A utility that automates parts of the migration from VMware ESX 2.x to VMware Infrastructure 3 (VI3) is a leading candidate for inclusion in VMware Inc.'s next
News of the migration utility, dubbed "Dmotion" internally, was leaked by a participant on one of VMware's own technology network (VMTN) discussion forums. With it, users will be able to move a virtual machine (VM) running in an ESX 2.x environment to ESX 3 without taking it down. A VMware representative did confirm that the company is working on Dmotion, and is "targeting" it for inclusion in 3.0.1.
VMware would not comment on the specifics of how Dmotion works, but people familiar with it say it appears to work by creating a snapshot of a running virtual machine to which new changes are written, using VMotion to copy the VM to an ESX 3 environment and, finally, applying the changes in the snapshot.
The hot VM upgrade capability will also have some limitations, specifically:
- Movement between ESX 2.x and VI3 will be "one-way."
- Users will eventually need to reboot their virtual machines to upgrade the virtual hardware (from VM2 to VM3 format) and install VMware Tools. Until that work is complete, VI3 features such as Consolidated Backup, Distributed Resource Scheduler (DRS) and VMwareHA will not work.
"Definitely worth the wait," wrote "d1c1ple," a senior systems engineer from New Jersey. "My co-worker and I sat in the VI3 update class a few weeks ago and our heads exploded when thinking of tackling one of our largest 2.5x farms. [This] should be a huge improvement if it works as advertised."
Indeed, the current process for moving from ESX 2 to 3 "isn't impossible -- it can be done -- but it's quite complex," said Mike Laverick, a freelance VMware instructor and trainer located in the U.K. and owner of the site www.rtfm-ed.co.uk.
According to a VMware white paper, "Planning an Upgrade to VMware Infrastructure 3", the move to VI3 involves upgrading these five key components:
- VirtualCenter, the management station, from 1.x to 2.x
- ESX Server, the hypervisor, from 2.x to 3.0
- VMFS, from VMFS 2 to VMFS 3
- The Virtual Machine files (from VM2 to VM3 format)
- VMware Tools
Upgrading also requires careful planning. VMware provides a pre-install perl script that users can run to discover things like whether they have enough free space or whether they are at the right patch level to perform the upgrade.
And in cases where multiple physical ESX servers share the same storage and LUNs, upgrading also requires a process VMware refers to as "host-VM-lun (HVL) alignment." With HVL alignment, "you migrate virtual machines so that all virtual machines on a given LUN are associated with only one server host," the white paper states. This prevents the upgrade of an ESX host or a VMFS file system from impacting a virtual machine running on another system.
Whatever the case, the upgrade process can currently take two basic forms, Laverick said: an in-place upgrade in which you take the system down and upgrade the components in order; or a migration upgrade in which you build a full ESX 3 environment in tandem with the ESX 2 and into which you cold-migrate old VMs. The addition of Dmotion would mean that the VMs could be moved into the new ESX 3 and VMFS 3 environment while they are running.
The in-place upgrade is fine for sites with just a few servers and that "can afford to have their environment down for the weekend," Laverick said. Large corporate users, on the other hand, most likely can't afford the downtime, and must do a staged a migration.
The downside to a migration upgrade, of course, is that you need an equivalent second system -- both servers as well as storage. And "storage," said Laverick, "is the nub of the issue."
"For some corporations, it's fine, because they have the extra storage," Laverick said. "But for others that are running their storage up to the hilt, they have to go out and buy much more." VMware, meanwhile, "tells you: 'If you don't have the storage [free space], go out and buy it for the migration, then use it for something else [when you're done].' That's fine, but what if you don't have another use for it?"
Third parties step in
In the interim, a couple of third-party software providers have stepped in and are offering tools that assist in the ESX 2.x to VI3 process. PlateSpin Ltd.'s PowerConvert is a generic tool for upgrading and migrating server platforms but also includes Automated V2V capabilities for migrating between ESX 2.1 and VI3. Vizioncore Inc. offers esxMigrator, which users its esxReplicator and esxRanger tools to automate all but the final reboot of the virtual machines.
Azeem Mohamed, senior director of marketing and products at Vizioncore, said that a lot of the trouble VMware customers have with VI3 upgrades "is in all the planning up front." VMware, he said, "really wanted to bring VI3 out as fast as possible." In their haste, "they published the [upgrade] methodology, but they stopped short of automating it."