Citrix Systems 6 manual Software iSCSI Support, Citrix StorageLink SRs

xe sr-create host-uuid=<valid_uuid>content-type=iso \ type=iso name-label=<"Example ISO SR"> \ device_config:location=<nfs server:path>>

Software iSCSI Support

XenServer provides support for shared SRs on iSCSI LUNs. iSCSI is supported using the open-iSCSI software iSCSI initiator or by using a supported iSCSI Host Bus Adapter (HBA). The steps for using iSCSI HBAs are identical to those for Fibre Channel HBAs, both of which are described in the section called “Creating a Shared LVM over Fibre Channel / iSCSI HBA or SAS SR (lvmohba)”.

Shared iSCSI support using the software iSCSI initiator is implemented based on the Linux Volume Manager (LVM) and provides the same performance benefits provided by LVM VDIs in the local disk case. Shared iSCSI SRs using the software-based host initiator are capable of supporting VM agility using XenMotion: VMs can be started on any XenServer host in a resource pool and migrated between them with no noticeable downtime.

iSCSI SRs use the entire LUN specified at creation time and may not span more than one LUN. CHAP support is provided for client authentication, during both the data path initialization and the LUN discovery phases.

XenServer Host iSCSI configuration

All iSCSI initiators and targets must have a unique name to ensure they can be uniquely identified on the network. An initiator has an iSCSI initiator address, and a target has an iSCSI target address. Collectively these are called iSCSI Qualified Names, or IQNs.

XenServer hosts support a single iSCSI initiator which is automatically created and configured with a random IQN during host installation. The single initiator can be used to connect to multiple iSCSI targets concurrently.

iSCSI targets commonly provide access control using iSCSI initiator IQN lists, so all iSCSI targets/LUNs to be accessed by a XenServer host must be configured to allow access by the host's initiator IQN. Similarly, targets/ LUNs to be used as shared iSCSI SRs must be configured to allow access by all host IQNs in the resource pool.

Note:

iSCSI targets that do not provide access control will typically default to restricting LUN access to a single initiator to ensure data integrity. If an iSCSI LUN is intended for use as a shared SR across multiple XenServer hosts in a resource pool, ensure that multi-initiator access is enabled for the specified LUN.

The XenServer host IQN value can be adjusted using XenCenter, or using the CLI with the following command when using the iSCSI software initiator:

xe host-param-set uuid=<valid_host_id> other-config:iscsi_iqn=<new_initiator_iqn>

Warning:

It is imperative that every iSCSI target and initiator have a unique IQN. If a non-unique IQN identifier is used, data corruption and/or denial of LUN access can occur.

Warning:

Do not change the XenServer host IQN with iSCSI SRs attached. Doing so can result in failures connecting to new targets or existing SRs.

Citrix StorageLink SRs

The Citrix StorageLink (CSL) storage repository provides direct access to native array APIs to offload intensive tasks such as LUN provisioning, snapshot and cloning of data. CSL provides a number of supported adapter types in order to communicate with array management APIs. Once successfully configured, the adapter will handle all provisioning and mapping of storage to XenServer hosts on demand. Data path support for LUNs includes both Fibre Channel and iSCSI as hardware permits.

CSL SRs can be created, viewed, and managed using both XenCenter and the xe CLI.

Note:

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