You can back up a managed server to a XenServer backup file (.xbk) that can then be used to restore the server in case of hardware failure. Note that this will back up just the server itself, but not any VMs that might be running on it.
We recommend that you back up your servers frequently to enable you to recover from possible server and/or software failure. When backing up servers in XenCenter, note the following points:
To restore a server, you can select and restore the backup file within XenCenter, and then you need to reboot the server from the XenServer installation CD to complete the restore.