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HP Integrity Virtual Machines Version 4.0 Installation, Configuration, and Administration > Chapter 10 Migrating Virtual Machines

Network and Storage Migration Considerations

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Effective migration of VM Host systems depends on proper configuration of the networks and storage used by the source and destination hosts. The hpvmmigrate command verifies that the source and destination hosts provide the guest with symmetric accessibility to network and storage resources. If you set up the configuration properly on both hosts before you migrate the guest, the migration task is much easier and faster.

Network Configuration Considerations

The source and destination hosts should be on the same subnet. The hpvmmigrate command preserves the MAC address of the guest being migrated. Thus, having the hosts on the same subnet prevents problems that can occur from changing the guest’s host name or IP address. With both hosts on the same subnet, the guest boots properly on the destination host.

In addition, ensure that all pNICs are symmetrically configured on both the source and destination hosts. For example, if lan0 on HostA is connected to subnet A, and lan1 is connected to subnet B, make sure that, on HostB, lan0 is connected to subnet A and lan1 is connected to subnet B.

Storage Configuration Considerations

Both the source and destination hosts must share access to symmetrically configured storage devices. The same storage devices must be visible to both the source host and destination hosts. The hpvmmigrate command uses the Fibre Channel worldwide identifier (WWID) to determine whether the storage allocated to a guest on the soure host is also reachable on the destination host. The new hpvmmigrate -t device translation option performs automatic mapping of device names when used with the -m option.

The hpvmmigrate command assumes that guests use storage area network (SAN) resources specified as whole-disk backing stores (for example, /dev/rdisk/disk2). File backing stores can also be used, but whole-disk LUN backing stores achieve significantly better run-time performance. Also, you can create virtual machines with direct attached storage (DAS), but guests that use DAS cannot be migrated.

To prevent migrating guests that are using the same resources at the same time on multiple VM Hosts, guests are disabled on the source VM Host when they are migrated to a destination VM Host. To avoid other accidental misuse of disk devices, mark as restricted all the disk devices that are used for guest storage on all hosts, except the disk that contains the guest. To mark a disk as restricted, use the hpvmdevmgmt command. For example:

# hpvmdevmgmt –a rdev:entry_name

The –a option accepts the name of the device to be restricted. For example:

# hpvmdevmgmt –a rdev:/dev/rdisk/disk0

For more information about the hpvmdevmgmt command, see Chapter 7.

Security Considerations

The hpvmmigrate command requires HP-UX Secure Shell (SSH) to be set up on both the source and destination host systems. SSH provides a secure communication path between hosts and is installed on HP-UX 11.23 systems by default. To enable secure communication between the source and destination hosts, you must generate SSH keys on both systems.

The hpvmmigrate command uses SSH public-key based authentication between the source and destination hosts. Password-based and host-based authentication are not supported.

You need root privileges to generate and set up the SSH keys required for guest migration.

SSH Key Setup

To set up the SSH keys on the source and destination hosts, HP recommends that you use the HP-UX Distributed Systems Administration Utilities (DSAU) tools which are installed by default on HP-UX 11.23 (0512 release). The bundle name is DSAUtilities.

To set up SSH keys between hosts, use the /opt/dsau/bin/csshsetup command. The csshsetup command simplifies the task of setting up SSH public-key authentication trust relationships between hosts. The –r (round-robin) option sets up bidirectional authentication. Round-robin key exchange establishes “any-member-to-any-member” authentication. For more information, see csshsetup.

Alternatively, SSH keys can be generated manually on the individual systems and then copied to the remote system's $HOME/.ssh/authorized_keys2 file by using the ssh_keygen command. The ssh_keygen command generates, manages, and converts authentication keys for SSH. It also creates RSA keys for use by the SSH protocol.

To use SSH with RSA or DSA authentication, the ssh_keygen command creates the authentication key in one of the following files:

  • $HOME/.ssh/identity

  • $HOME/.ssh/id_dsa

  • $HOME/.ssh/id_rsa

The system administrator may also use the ssh_keygen command to generate host keys, as seen in /etc/rc. For more information about SSH key generation, see ssh-keygen.

Table 10-2 lists the files that are modified or created for RSA key generation.

Table 10-2 RSA Key Files

File NameFile Contents
$HOME/.ssh2/id_rsaDefault RSA private key for the user
$HOME/.ssh2/id_rsa.pubDefault RSA public key for the user
$HOME/.ssh/authorized_keysNames of the host RSA public keys that can authenticate to this account

 

Troubleshooting SSH Key Setup

If the SSH is installed on both the source and the destination system, you can run the ssh command on the source host to establish a connection to the destination host. This action ensures that SSH keys are set up between the two hosts. The following error message can result from having SSH keys set up improperly:

Error: hpvmmigrate: SSH execution error. Error: hpvmmigrate: Remote execution error on destination-host.
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