Update – read to the end, I just got some news on some…limitations.

Update #2 - All API restrictions have been removed with v3.5U3!

Update #3 - false alarm According to Mike D, this was an accident and it’ll be turned off in U4.

Have you checked out VMware’s free ESXi hypervisor yet?  It’s some pretty neat stuff, taking most of the high perf features we know and love from its big brother and wrapping them in a tiny package. It’s a great tool which I’ve started to get into lately (we have an existing VI3 ESX shop).

One thing you cannot do with the free version however, is connect to and manage multiple host systems at the same time.  The VI Client is great, but it’s scope is limited to a single server.  If you happen to have a VirtualCenter, you’ll find that you can’t add an ESXi server to your farm—it fails due to a missing license.

Not all is lost!  Late in the dev cycle of VMware’s VI Toolkit (for Windows), they added a Server parameter to every cmdlet. Let me show you how you can use it to control multiple ESXi servers at once—for free.  You can’t beat free.

PS > $esxi = Connect-VIServer 192.168.0.51,192.168.0.55 -Credential (Get-Credential)

cmdlet Get-Credential at command pipeline position 1
Supply values for the following parameters:
Credential
PS > $esxi

Name                           Port                           User
----                           ----                           ----
192.168.0.51                   443                            root
192.168.0.55                   443                            root

PS > $DefaultVIServer

Name                           Port                           User
----                           ----                           ----
192.168.0.55                   443                            root

PS > (Get-VM | Measure-Object).Count
7
PS > (Get-VM -Server $esxi | Measure-Object).Count
10

Note that if you leave off the Server param, the cmdlets will operate on the most recently-connected server, which will be stored automatically in the $DefaultVIServer variable.

Limitations to Management API in ESXi

I just learned from the product group that most of the objects exposed by the VI API in the free edition are read-only.  This is pretty harsh.  This means your reporting scenarios will still work well, but you can forget about ongoing maintenance. I’ll probably post a follow up to this article once I have a better handle on what you can and can’t do.  Stay tuned.

Update @ 12/14/08 - With version 3.5U3, VMware has thankfuilly decided to remove all API restrictions. See this article.