Specifications

The upgrade to vCenter Server 5.x might also fail from a lack of sufficient memory if you use a DNS load
balancing solution with shared datastores. In a large vCenter Server database, the conversion of datastore
paths to the new format can require a large amount of memory. See the VMware Knowledge Base article at
http://kb.vmware.com/kb/2015055.
About the vCenter Host Agent Pre-Upgrade Checker
The vCenter Host Agent Pre-Upgrade Checker produces a report showing known issues that might prevent
a successful upgrade of the vCenter Host Agent software.
To ensure a successful upgrade to vCenter Server 5.x, you must diagnose and fix any potential problems on
the managed ESX/ESXi hosts. You can run the vCenter Host Agent Pre-Upgrade Checker for in-place
upgrades from vCenter Server 4.x to vCenter Server 5.x.
vCenter Host Agent runs on all managed ESX/ESXi hosts. This software coordinates actions received from
vCenter Server. When you add a host to vCenter Server, the agent is installed on the physical ESX/ESXi host.
When you upgrade to vCenter Server 5.x, the agent residing on each ESX/ESXi host must be upgraded as
well.
During a vCenter Server upgrade, the existing agent software is uninstalled and the updated agent software
is installed in its place. If the upgrade fails, the updated agent software might not be installed and the host
might become unreachable by vCenter Server 4.x or 5.x. To avoid this condition, you can run the vCenter
Host Agent Pre-Upgrade Checker before you try to upgrade to vCenter Server 5.x.
The vCenter Host Agent Pre-Upgrade Checker checks to make sure that the agent software is ready to be
upgraded. Some of the checks include checking to make sure that the host is reachable, the disk space is
sufficient, the network is functioning, the file system is intact, and required patches are applied. Each time
you run the tool, the system queries VMware.com and downloads any new updates for the tool. This action
ensures that as new upgrade issues are discovered, the tool remains as useful as possible.
IMPORTANT A successful vCenter Host Agent pre-upgrade check does not guarantee a successful upgrade to
vCenter Server 5.x. An upgrade to vCenter Server involves multiple components, and the tool checks only
one component: the vCenter Host Agent. Also, the tool checks only known issues. Other issues might be
present that the tool does not check.
The vCenter Host Agent Pre-Upgrade Checker does not fix the reported issues. You must resolve the
reported issues manually and rerun the tool to verify that the issues are resolved.
For the procedure to run the vCenter Host Agent Pre-Upgrade Checker, see “Run the vCenter Host Agent
Pre-Upgrade Checker,” on page 57.
Run the vCenter Host Agent Pre-Upgrade Checker
The vCenter Host Agent Pre-Upgrade Checker reports known issues that might prevent a successful
upgrade of the vCenter Host Agent software.
For more information about the vCenter Host Agent Pre-Upgrade Checker, see “About the vCenter Host
Agent Pre-Upgrade Checker,” on page 57.
Prerequisites
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Verify that the ESX/ESXi hosts are managed by vCenter Server.
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Verify that the vCenter Host Agent software is running on each managed ESX/ESXi host.
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Verify that you have Internet connectivity from the vCenter Server system. This allows new updates to
be applied to the tool and allows you to view the reports and the Knowledge Base (KB) articles
associated with the reports.
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Download the vCenter Server installer. See “Download the vCenter Server Installer,” on page 59.
Chapter 3 Preparing for the Upgrade to vCenter Server
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