6.5.1

Table Of Contents
Verify that any Windows host machine on which vCenter Server runs is synchronized with the Network
Time Server (NTP) server. See the Knowledge Base article http://kb.vmware.com/kb/1318.
To synchronize ESXi clocks with an NTP server, you can use the VMware Host Client. For information
about editing the time configuration of an ESXi host, see vSphere Single Host Management.
Synchronize ESXi Clocks with a Network Time Server
Before you install vCenter Server or deploy the vCenter Server Appliance, make sure all machines on
your vSphere network have their clocks synchronized.
This task explains how to set up NTP from the VMware Host Client. You can instead use the vicfg-ntp
vCLI command. See the vSphere Command-Line Interface Reference.
Procedure
1 Start the VMware Host Client, and connect to the ESXi host.
2 Click Configure.
3 Under System, click Time Configuration, and click Edit.
4 Select Use Network Time Protocol (Enable NTP client).
5 In the Add NTP Server text box, enter the IP address or fully qualified domain name of one or more
NTP servers to synchronize with.
6 (Optional) Set the startup policy and service status.
7 Click OK.
The host synchronizes with the NTP server.
Downtime During the vCenter Server Upgrade
When you upgrade vCenter Server, downtime is required for vCenter Server.
Expect downtime for vCenter Server as follows:
n
The upgrade requires vCenter Server to be out of production for a minimum of 40 to 50 minutes, and
can take much longer depending on the size of the database. The database schema upgrade takes
approximately 10 to 15 minutes of this time. This estimate does not include host reconnection time
after the upgrade.
n
For vCenter Server deployments with an embedded database, the upgrade can require extra time to
migrate the data from the legacy vCenter Server database to the new database instance.
n
If Microsoft .NET Framework is not installed on the machine, a restart is required before starting the
vCenter Server installation.
n
vSphere Distributed Resource Scheduler (DRS) does not work while the upgrade is in progress.
vSphere HA does work during the upgrade.
Downtime is not required for the ESXi hosts that vCenter Server is managing, or for virtual machines that
are running on the hosts.
vSphere Upgrade
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