You can use the Rolling Pool Upgrade wizard to upgrade XenServer hosts - hosts in a pool or standalone hosts to a newer version.
The wizard guides you through the upgrade procedure and organizes the upgrade path automatically. For pools, each of the hosts in the pool is upgraded in turn, starting with the pool master. Before starting an upgrade, the wizard conducts a series of prechecks to ensure that certain pool-wide features, such as HA and WLB, are temporarily disabled and that each host in the pool is prepared for upgrade (for example, that the CD/DVD drive of each host is empty). Only one host is offline at a time, and any running VMs are automatically migrated off each host before the upgrade is installed on that host.
The wizard can operate in manual or automatic mode:
You can also use the Rolling Pool Upgrade wizard to upgrade standalone hosts, that is, hosts which are not in a pool.
Upgrading a pool of XenServer hosts requires careful planning. As you plan your upgrade, it is very important to be aware of the following:
Once you have selected your Upgrade Mode, click Run Prechecks.