Using Storage
XenMotion, a running virtual machine can be moved from one server to another
server in the same resource pool with virtually no service interruption. The
choice of destination server depends on how the VM and the pool are configured.
XenCenter allows you
move VMs that are not currently running, to a new storage in the same pool
using the
Move
VM dialog box. To move a VM: from the XenCenter menu, click
VM and then
Move
VM. Select a storage repository to which you would like to move the
VM to and click
Move.
About VM
migration with XenMotion and Storage XenMotion
XenMotion
XenMotion is
available in all versions of XenServer and allows you to move a running VM from
one host to another host, when the VMs disks are located on storage shared by
both hosts. This allows for pool maintenance features such as Workload
Balancing (WLB), High Availability (HA), and Rolling Pool Upgrade (RPU) to
automatically move VMs. These features allow for workload leveling,
infrastructure resilience, and the upgrade of server software, without any VM
downtime. Storage can only be shared between hosts in the same pool, as a
result, VMs can only be moved within the same pool.
Storage XenMotion
Storage XenMotion
additionally allows VMs to be moved from one host to another, where the VMs are
not located on storage shared between the two hosts. As a result, VMs stored on
local storage can be migrated without downtime and VMs can be moved from one
pool to another. This enables system administrators to:
- rebalance VMs between
XenServer pools (for example from a development environment to a production
environment).
- upgrade and update
standalone XenServer hosts without any VM downtime.
- upgrade XenServer host
hardware.
Note: Moving a VM
from one host to another preserves the VM state. The state information includes
information that defines and identifies the VM as well as the historical
performance metrics, such as CPU and network usage.
Storage XenMotion
also allows you to move virtual disks from one Storage Repository (SR) to a
different SR within the same pool. For more information, see
Move Virtual Disks.
Compatibility
requirements
When migrating a
VM with XenMotion or Storage XenMotion, the new VM host must meet the following
compatibility requirements in order for the migration to proceed:
- XenServer Tools must be
installed on each VM that you wish to migrate.
- The target host must have
the same or a more recent version of XenServer installed as the source host.
- For Storage XenMotion, if
the CPUs on the source host and target host are different, the target host must
provide at least the entire feature set as the source host's CPU. Consequently,
it is unlikely to be possible to move a VM between, for example, AMD and Intel
processors.
- For Storage XenMotion, VMs
with more than one snapshot cannot be migrated.
- For Storage XenMotion, VMs
with more than six attached VDIs cannot be migrated.
- The target host must have
sufficient spare memory capacity or be able to free sufficient capacity using
Dynamic Memory Control. If there is not enough memory, the migration will fail
to complete.
- For Storage XenMotion, the
target storage must have enough free disk space (for the VM and its snapshot)
available for the incoming VMs. If there is not enough space, the migration
will fail to complete.
XenMotion and Storage
XenMotion limitations
XenMotion and
StorageXenMotion are subject to the following limitations:
- Storage XenMotion must not
be used in XenDesktop deployments.
- VMs using PCI pass-thru
cannot be migrated.
- VM performance will be
reduced during migration.
- For Storage XenMotion,
pools protected by High Availability (HA) or Work Load Balancing (WLB) should
have HA and WLB disabled before attempting VM migration.
- Time to completion of VM
migration will depend on the memory footprint of the VM, and its activity, in
addition, VMs being migrated with Storage XenMotion will be affected by the
size of the VDI and its storage activity.
- VMs with VDIs located on
StorageLink SRs cannot be migrated.
Important: StorageLink technology has been removed from
XenServer version 6.5 and higher. Applications, code, or usage that depend on
StorageLink technology will not function in XenServer version 6.5 and higher.
For information about migrating existing virtual disks (VDIs) from a
StorageLink SR to an iSCSI or Fibre Channel SR, see
CTX141433.