HP BL680c XenServer Administrator's Guide 4.1.0 - Page 13

Coping with machine failures

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XenServer Hosts and resource pools Note • Do not create the backup in domain 0. • This procedure may create a large backup file. • To complete a restore you may have to reboot to the original install CD. • This data can only be restored to the original machine. Procedure 2.7. To backup a VM 1. Ensure that the VM to be backed up is offline. 2. Run the command: xe vm-export vm=vm-uuid filename=backup Note This backup also backs up all of the VM's data. When importing a VM, you can specify the storage mechanism to use for the backed updata. Warning Because this process backs up all of the VM's data, it can take some time to complete. Procedure 2.8. To backup VM metadata only • Run the command: xe vm-export vm=vm-uuid filename=backup --metadata 2.7. Coping with machine failures This section provides details of how to recover from various failure scenarios. All failure recovery scenarios require the use of one or more of the backup types listed in the Section 2.6, "Backups". 2.7.1. Member failures Master nodes detect the failures of members by receiving regular heartbeat messages. If no heartbeat has been received for 200 seconds, the master assumes the member is dead. There are two ways to recover from this problem: • Repair the dead member (e.g. by physically rebooting it). When the connection to the member is restored, the master will mark the member as alive again. • Instruct the master to forget about the member node using the xe host-forget CLI command. Once the member has been forgotten, all the VMs which were running there will be marked as offline and can be restarted on other XenServer Hosts. Note it is very important to ensure that the XenServer Host is actually offline, otherwise VM data corruption might occur. Be careful not to split your pool into multiple pools of a single host by using xe host-forget, since this could result in them all mapping the same shared storage and corrupting VM data as well. 7

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XenServer Hosts
and resource pools
7
Note
•
Do not create the backup in domain 0.
•
This procedure may create a large backup file.
•
To complete a restore you may have to reboot to the original install CD.
•
This data can only be restored to the original machine.
Procedure 2.7. To backup a VM
1.
Ensure that the VM to be backed up is offline.
2.
Run the command:
xe vm-export vm=
vm-uuid
filename=
backup
Note
This backup also backs up all of the VM's data. When importing a VM, you can specify the storage
mechanism to use for the backed updata.
Warning
Because this process backs up all of the VM's data, it can take some time to complete.
Procedure 2.8. To backup VM metadata only
•
Run the command:
xe vm-export vm=
vm-uuid
filename=
backup
--metadata
2.7. Coping with machine failures
This section provides details of how to recover from various failure scenarios. All failure recovery scenarios
require the use of one or more of the backup types listed in the Section 2.6, “Backups”.
2.7.1. Member failures
Master nodes detect the failures of members by receiving regular heartbeat messages. If no heartbeat has
been received for 200 seconds, the master assumes the member is dead. There are two ways to recover
from this problem:
•
Repair the dead member (e.g. by physically rebooting it). When the connection to the member is restored,
the master will mark the member as alive again.
•
Instruct the master to forget about the member node using the
xe host-forget
CLI command. Once the
member has been forgotten, all the VMs which were running there will be marked as offline and can be
restarted on other XenServer Hosts. Note it is
very
important to ensure that the XenServer Host is actually
offline, otherwise VM data corruption might occur. Be careful not to split your pool into multiple pools of a
single host by using
xe host-forget
, since this could result in them all mapping the same shared storage
and corrupting VM data as well.