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xe vm-export vm=<vm_uuid> filename=<backup> --metadata
Full metadata backup and disaster recovery (DR)
This section introduces the concept of Portable Storage Repositories (Portable SRs), and explains how they
work and how to use them as part of a DR strategy.
DR and metadata backup overview
XenServer 5.6 introduces the concept of Portable SRs. Portable SRs contain all of the information necessary
to recreate all the Virtual Machines (VMs) with Virtual Disk Images (VDIs) stored on the SR after re-attaching
the SR to a different host or pool. Portable SRs can be used when regular maintenance or disaster recovery
requires manually moving a SR between pools or standalone hosts.
Using portable SRs has similar constraints to XenMotion as both cases result in VMs being moved between
hosts. To use portable SRs:
• The source and destination hosts must have the same CPU type and networking configuration. The
destination host must have a network of the same name as the one of the source host.
• The SR media itself, such as a LUN for iSCSI and FibreChannel SRs, must be able to be moved, re-
mapped, or replicated between the source and destination hosts
• If using tiered storage, where a VM has VDIs on multiple SRs, all required SRs must be moved to the
destination host or pool
• Any configuration data required to connect the SR on the destination host or pool, such as the target IP
address, target IQN, and LUN SCSI ID for iSCSI SRs, and the LUN SCSI ID for FibreChannel SRs, must
be maintained manually
• The backup metadata option must be configured for the desired SR
Note:
When moving portable SRs between pools the source and destination pools are not required to have the
same number of hosts. Moving portable SRs between pools and standalone hosts is also supported provided
the above constraints are met.
Portable SRs work by creating a dedicated metadata VDI within the specified SR. The metadata VDI is used
to store copies of the pool or host database as well as the metadata describing the configuration of each
VM. As a result the SR becomes fully self-contained, or portable, allowing it to be detached from one host
and attached to another as a new SR. Once the SR is attached a restore process is used to recreate all of
the VMs on the SR from the metadata VDI. For disaster recovery the metadata backup can be scheduled
to run regularly to ensure the metadata SR is current.
The metadata backup and restore feature works at the command-line level and the same functionality is
also supported in xsconsole. It is not currently available through XenCenter.
Backup and restore using xsconsole
When a metadata backup is first taken, a special backup VDI is created on a SR. This VDI has an ext3
filesystem that stores the following versioned backups:
• A full pool-database backup.
• Individual VM metadata backups, partitioned by the SRs in which the VM has disks.
• SR-level metadata which can be used to recreate the SR description when the storage is reattached.
