User's Manual

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.