Citrix Systems 5.6 Software iSCSI Support

Note:

This works on new VDI creation in the selected FlexVol, or on all FlexVols during an SR scan and overrides

any manual size adjustments made by the administrator to the SR FlexVols.

To create a NetApp SR, use the following command.

xe sr-create host-uuid=<valid_uuid> content-type=user \

name-label=<"Example shared NetApp SR"> shared=true \

device-config:target=<192.168.1.10> device-config:username=<admin_username> \

device-config:password=<admin_password> \

type=netapp

Due to the complex nature of mapping VM storage objects onto NetApp storage objects such as LUNs,

FlexVols and disk Aggregates, the plugin driver makes some general assumptions about how storage

objects should be organized. The default number of FlexVols that are managed by an SR instance is 8,

named XenStorage_<SR_UUID>_FV<#> where # is a value between 0 and the total number of FlexVols

assigned. This means that VDIs (LUNs) are evenly distributed across any one of the FlexVols at the point that

the VDI is instantiated. The only exception to this rule is for groups of VM disks which are opportunistically

assigned to the same FlexVol to assist with VM cloning, and when VDIs are created manually but passed a

vmhint flag that informs the backend of the FlexVol to which the VDI should be assigned. The vmhint may

be a random string, such as a uuid that is re-issued for all subsequent VDI creation operations(to ensure

grouping in the same FlexVol), or it can be a simple FlexVol number to correspond to the FlexVol naming

convention applied on the Filer. Using either of the following 2 commands, a VDI created manually using

the CLI can be assigned to a specific FlexVol:

xe vdi-create uuid=<valid_vdi_uuid> sr-uuid=<valid_sr_uuid> \

sm-config:vmhint=<valid_vm_uuid>

xe vdi-create uuid=<valid_vdi_uuid> sr-uuid=<valid_sr_uuid> \

sm-config:vmhint=<valid_flexvol_number>

Cloning a VDI entails generating a snapshot of the FlexVol and then creating a LUN clone backed off the

snapshot. When generating a VM snapshot you must snapshot each of the VMs disks in sequence. Because

all the disks are expected to be located in the same FlexVol, and the FlexVol snapshot operates on all

LUNs in the same FlexVol, it makes sense to re-use an existing snapshot for all subsequent LUN clones. By

default, if no snapshot hint is passed into the backend driver it will generate a random ID with which to name

the FlexVol snapshot. There is a CLI override for this value, passed in as an epochhint. The first time

the epochhint value is received, the backend generates a new snapshot based on the cookie name. Any

subsequent snapshot requests with the same epochhint value will be backed off the existing snapshot:

xe vdi-snapshot uuid=<valid_vdi_uuid> driver-params:epochhint=<cookie>

During NetApp SR provisioning, additional disk space is reserved for snapshots. If you plan to not use the

snapshotting functionality, you might want to free up this reserved space. To do so, you can reduce the value

of the other-config:multiplier parameter. By default the value of the multiplier is 2.4, so the amount

of space reserved is 2.4 times the amount of space that would be needed for the FlexVols themselves.

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