Is upgrading from ESXi 3.5 to 4.1 possible or do I have to hit 4 first?

Posted on 2010-09-22
Last Modified: 2012-06-27
Just wondering if I am supposed to update to 4 first.  I have googled around and got conflicting answers.
Question by:cjameson74
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LVL 11

Accepted Solution

willettmeister earned 125 total points
ID: 33738125
I would recommend a clean install and not an upgrade.  
LVL 26

Assisted Solution

lnkevin earned 250 total points
ID: 33738473
Upgrade is a mess since it will overwrite the kernel anyway. Re-install should be a proper way to move from version to other version.


Assisted Solution

simonseztech earned 125 total points
ID: 33738673
Hello,First be sure that your hardware is on the Hardware Compatiblity List for 4.1 the ESX 3.x host has network access, you can use the vSphere Host Update Utility to perform the upgrade.  vCenter Update Manager is available with vCenter Server 4.0, vCenter Server 4.0 Update 1, vCenter Server 4.0 Update 2, and vCenter Server 4.1. Is available on the vSphere download site: can perform an "offline" update following this guide advise that this currently experimental support.Since you are upgrading please consider upgrading to ESXi 4.1, because ESX 4.1 is the lastest build of the ESX line. From now on VMware will only support and update ESXi.The official upgrade guide is at: and all of the other docs including an HTML based library at: it helpfrom previous similar question:
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LVL 26

Assisted Solution

lnkevin earned 250 total points
ID: 33738809
Do not update, you will be running in some API error issues with some component especially qlogic drivers... you just install ESXi 4.5 (re-install the OS). If you currently have some vm's on it, make sure you enable the option keep all vm....


Expert Comment

by:Matthew England
ID: 33739674
Looks like you've got some pretty good answers already posted, but I figured since I ran in to the same situation I'd comment. ESXi 3.5 will not upgrade to 4.0 or higher. Starting at ESXi 4.0, the vSphere Host Update Utility will patch and upgrade your hosts, but 3.5 to 4.0+ will require a clean install.
LVL 42

Expert Comment

ID: 33740616
You have some good answers so far.  Keep in mind, vCenter 4.1 (if you're using it) requries a 64 bit OS so you can't upgrade vCenter 2.5 to 4.1 unless you're running on 64 bit OS for it.


Author Closing Comment

ID: 33740642
I got enough answers here to base my decision

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