Citrix Systems 5.6 manual Software iSCSI Support, Managing VDIs in a NetApp SR

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

Managing VDIs in a NetApp SR

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>

Taking VDI snapshots with a NetApp SR

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:multiplierparameter. 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

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