Archive:Citrix XEN Server en

THE CONTENT OF THIS PAGE IS OUTDATED

SEP AG has discontinued support for obsolete SEP sesam versions. Instructions are still available for these SEP sesam products, however, SEP AG accepts no responsibility or liability for any errors or inaccuracies in the instructions or for the incorrect operation of obsolete SEP sesam software. It is strongly recommended that you update your SEP sesam software to the latest version. For the latest version of SEP sesam documentation, see documentation home.

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Introduction

The SEP sesam extension for Citrix XenServer provides hot (online) and cold (offline) backups of virtual machines (VMs) running on a Citrix XenServer. Consistent backup is achieved by creating a snapshot of the virtual machine. After creation, the snapshot is exported to a SEP sesam backup medium. VSS writers on Windows VMs are notified before snapshot creation so all VSS aware applications like MS-SQL are brought into a consistent state.

System Requirements

SEP sesam OS and Database Support Matrix
SEP sesam Server
Citrix XEN backup client is included in all SEP sesam packages

On XenServer

No special requirements are needed for the XenServer side.

On a DataMover (SDM-CX)

For details on requirements, see SEP sesam DataMover for Citrix XenServer (SDM-CX) . A data mover role for Citrix XenServer can be combined either with a SEP sesam Server, SEP sesam Remote Device Server or a SEP sesam Client. Any of these can serve as a SEP sesam data mover (SDM-CX) to transfer (send or receive) data between SEP sesam Server and Citrix XenServer.

Configuring XenServer as a SEP sesam Client

Check the following prerequisites before adding your XenServer to SEP sesam environment:

Each XenServer must have a dedicated management interface.
IMPORTANT: The backup traffic always goes over the management interface of the XenServer. Make sure you get good network performance, for example 2x 10Gbit network interfaces as a bond on the XenServer as well as on the backup server.
In a cluster configuration where more XenServers are organized in a pool, the pool master XenServer must be configured as a SEP sesam Client.

To protect your virtual machines, you must configure your XenServer as a SEP sesam Client. The options for configuring XenServer may differ slightly depending on your SEP sesam version.

From Main Selection -> Components -> Topology, select the relevant location and click the New client button. The New client window opens.
In the New client window, enter the management interface DNS name of the pool master otherwise browsing the XEN system will not work!
Under Operating system drop-down list, select the Citrix XenServer.
As of SEP sesam v. 4.4.3, the only supported access mode is PROXY, which is set by default when the Citrix XenServer operating system is selected.

	Note
	If you are using SEP sesam version ≥ 4.4.3, make sure that the PROXY access mode is selected. If the access mode CTRL is used, an error occurs when SEP sesam Server checks the connection to the SEP sesam XenServer client.

Click the tab Citrix XenServer and enter root/admin credentials for XenServer.
Select a data mover. The data mover must be the hostname of the SEP sesam Server or a non-Citrix XEN client. For details on requirements, see SEP sesam DataMover for Citrix XenServer (SDM-CX) .

Click OK to add the new client.

Backup

Backup of the VM's and XEN Templates

Create a new backup task in the SEP sesam GUI with task type Citrix XenServer. As backup source specify the display name of the virtual machine. By selecting the source, the backup type and task name are set automatically.

The Virtual Machine can be selected with the client file system browser under Citrix XenServer.

You can also get the name from XEN Center or on the XEN Server by executing command:

 xe vm-list

Attention: Only ONE VM can be saved by one backup task.

The backup is done online. If XenServer tools are installed on VM VSS-Writers are executed before making the snapshot.

Backup Type

Backup Type: Copy

Only a "Copy" VM backup can be performed with Citrix XenServer. FULL, DIFF, INC backups are not possible!

Meta data backup

Create a new backup task for the XEN Master with task type Citrix XenServer. As backup source type in "meta-data". Citrix recommends that you frequently perform this backup task at minimum once per day to recover from possible server and / or software failure. This backup includes the XEN Server pool database and the needed meta data of the pool.

Host data backup

Create a new backup task for each XEN Host with task type Citrix XenServer. As backup source type in "host-backup". This backup is a filebackup of the XEN Hypervisor without the VM's.

Restore of virtual machines

The restore is quite similar to a regular file system restore.

There are 2 different restore options:

with overwrite: the existing VM is destroyed and the backup is imported. The MAC address is the same as during backup.

without overwrite: A new VM name has to be specified as target. The backup is imported without any effect on the running VM. The MAC address of a restored VM is newly created.

Restore options

Recover after restore: Registers the VM after restore on XenServer and with it in XenCenter
Recover and online: Registers and starts the VM and brings it online

You must have a default storage repository defined, otherwise the restore will fail.

VM will always be imported

In the current implementation VM is always registered after the restore.

Check original VM name during restore

During a restore with the option overwrite the original VM is deleted even if another name for the target VM is specified.

Restore of XEN Host Systems

In case you want to restore a XenServer Host from a specific backup, restore the host-backup created with SEP Sesam to a random linux machine, be sure to restore the file as regular file restore like shown in this screenshot:

After you have restored the file, copy it to the XEN System and execute the following command:

xe host-restore file-name=<host_backup_filename>

This restores the compressed image back to the hard disk of the XenServer Host. In this context “restore” is something of a misnomer, as the word usually suggests that the backed-up state has been put fully in place. The restore command here only unpacks the compressed backup file and restores it to its normal form, but it is written to another partition (/dev/sda2) and does not overwrite the current version of the filesystem.

To actually use the restored version of the root filesystem, you need to reboot the XenServer Host using the XenServer installation CD and select the Restore from backup option.

After the Restore from Backup is completed, reboot the XenServer Host machine and it will start up from the restored image.

File System Option

SEPsesam license for Citrix Xen Server includes a Client backup license for every licensed VM seat to do a file level backup from this VM. To do this, a normal Sesam client has to be installed in the VM and the client has to be configured over GUI.

https connection

SEP sesam commonly uses http to transfer data from XenServer to SEP sesam server for reasons of speed. Backups over https can cause up to 98 % CPU load on XenServer. The use of https can be forced by entering the following option under 'task->properties->backup options:

 -a http=https

Troubleshooting

Message "Upload to URL ... failed" appears during restore

One possible reason for this message could be, that the default storage does not have sufficient disk space available. In this case another default storage has to be chosen via the XenCenter, which has enough free disk capacity to store the virtual disk(s).

SR_BACKEND_FAILURE_44: : There is insufficient space to create snapshot on SR http://support.citrix.com/article/CTX134910

Some errors are not reported in detail by XEN API. More information can be found in XenServer in /var/log directory.

In some pool configurations all pool members must have their management interface listed in dns.

If the settings below don't agree asynchronous routing and connection drops and/or 3 second or 80 second delays opening sockets may occour. This is very similar to having 2 network cards configured with ipv4 to the same subnet and connected to the same switch.

If you use Cisco Switches and you have configured (Citrix Unsupported) lacp bonding 802.3ad it is very important that both sides agree on the balancing type. The linux default is layer2 and the Cisco default is layer3+4.

Check the bonding mode on the host with cat /proc/net/bond/bond* for Bonding Mode: IEEE 802.3ad Dynamic link aggregation

Transmit Hash Policy: layer2 (0) or Transmit Hash Policy: layer3+4 (1).

Users have reported that this command and a reboot solves the problem but we cannot formally recommend it due to the untested and unsupported status:

xe pif-param-set uuid=${UUID_OF_BOND_PIF} other-config:bond-xmit_hash_policy=1

In the common situation where 802.1ad with xmit_hash_policy=1 and STP are in use multiple settings need to be adjusted on the Cisco side according to this document: http://support.citrix.com/article/CTX123158

Most other network related performance and reliability issues can be resolved with http://support.citrix.com/article/CTX123158

In some situations when using thin storage repositories an sr rescan is necessary to re-detect free space before a backup or restore ( This feature will be automated soon )