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dm-multipath tools in linux, device mapper nodes are not automatically created for all LUNs on the
system, and it is only when LUNs are actively used by the storage management layer that new device
mapper nodes are provisioned. It is unnecessary therefore to use any of the dm-multipath CLI tools to
query or refresh DM table nodes in XenServer. Should it be necessary to query the status of device-mapper
tables manually, or list active device mapper multipath nodes on the system, use the mpathutil utility:
• mpathutil list
• mpathutil status
Unlike the standard dm-multipath tools in Linux, device mapper nodes are not automatically created for
all LUNs on the system. As LUNs are actively used by the storage management layer, new device mapper
nodes are provisioned. It is unnecessary to use any of the dm-multipath CLI tools to query or refresh
DM table nodes in XenServer.
Note:
Due to incompatibilities with the integrated multipath management architecture, the standard dm-
multipath CLI utility should not be used with XenServer. Please use the mpathutil CLI tool for querying
the status of nodes on the host.
Note:
Multipath support in Equallogic arrays does not encompass Storage IO multipathing in the traditional
sense of the term. Multipathing must be handled at the network/NIC bond level. Refer to the Equallogic
documentation for information about configuring network failover for Equallogic SRs/LVMoISCSI SRs.
Storage Repository Types
The storage repository types supported in XenServer are provided by plugins in the control domain; these
can be examined and plugins supported third parties can be added to the /opt/xensource/sm directory.
Modification of these files is unsupported, but visibility of these files may be valuable to developers and
power users. New storage manager plugins placed in this directory are automatically detected by XenServer.
Use the sm-list command (see the section called “Storage Manager commands”) to list the available SR
types.
New storage repositories are created using the New Storage wizard in XenCenter. The wizard guides
you through the various probing and configuration steps. Alternatively, use the sr-create command. This
command creates a new SR on the storage substrate (potentially destroying any existing data), and creates
the SR API object and a corresponding PBD record, enabling VMs to use the storage. On successful creation
of the SR, the PBD is automatically plugged. If the SR shared=true flag is set, a PBD record is created
and plugged for every XenServer Host in the resource pool.
All XenServer SR types support VDI resize, fast cloning and snapshot. SRs based on the LVM SR type
(local, iSCSI, or HBA) provide thin provisioning for snapshot and hidden parent nodes. The other SR types
support full thin provisioning, including for virtual disks that are active.
Note:
Automatic LVM metadata archiving is disabled by default. This does not prevent metadata recovery for LVM
groups.
Warning:
When VHD VDIs are not attached, for example in the case of a VDI snapshot, they are stored by default thinly-
provisioned. Because of this it is imperative to ensure that there is sufficient disk-space available for the VDI
to become thickly provisioned when attempting to attach it. VDI clones, however, are thickly-provisioned.
