Product Documentation

StorageLink Storage

Oct 01, 2014
Important: StorageLink technology has been removed from XenServer version 6.5 and higher. Applications, code, or usage that depend on StorageLink technology will not function in XenServer version 6.5 and higher. For information about migrating existing virtual disks (VDIs) from a StorageLink SR to an iSCSI or Fibre Channel SR, see CTX141433.

A StorageLink SR can provide direct access to high-performance storage, allowing the VMs in your XenServer environment to benefit from array-side enterprise storage services such as replication, de-duplication, thin provisioning, snapshots and cloning, data protection, and performance optimization.

StorageLink SRs use storage adapters to access different storage arrays on all common storage technologies including both NAS and SAN over either Fibre Channel or iSCSI. The features available on a given StorageLink SR depend on the capabilities of the underlying array. StorageLink SRs can co-exist with other SR types on the same storage array hardware, and multiple StorageLink SRs can be defined within the same resource pool.

Depending on your environment and goals, StorageLink provides three advantages:

By default, the XenServer block device-based storage inserts a Logical Volume manager on a disk, either a locally attached device (LVM type SR) or a SAN-attached LUN over either Fibre Channel (LVMoHBA type SR), iSCSI (LVMoISCSI type SR) or SAS (LVMoHBA type SR). When you use StorageLink to configure an SR, LUNs are directly mapped to virtual machines as VDIs. As a result, the array storage abstraction matches the VDI storage abstraction, which is helpful in environments that manage storage provisioning at an array level.

Note: StorageLink SRs are not supported with XenDesktop.

Methods of Creating StorageLink SRs

There are two methods of creating StorageLink SRs: allowing StorageLink to create the volume (default) or creating the volume in advance. The default method of creating SRs with StorageLink may not be optimal in all environments.

StorageLink-created Volumes (Default)
The standard (default) method of creating SRs with StorageLink is to select an aggregate in the SR creation wizard and then allow StorageLink to create the volume and LUN for you automatically. When you use this method, each VDI gets a LUN in a unique volume. However, in environments that want to create many VDIs, this may not be ideal since you can end up with numerous volumes. Some storage vendors have a maximum recommended limit of number of volumes per storage array. Likewise, when you create an SR with StorageLink, the volume names are auto-generated so they are not easy-to-read or meaningful, which can complicate management. This method also limits your ability to use deduplication to reduce space consumed by common data (such as operating systems or applications) in the volume.
Pre-created Volumes
The best practice method of creating SRs with StorageLink is to specify a previously created volume by selecting the Show All button in the XenCenter SR wizard. This method enables each virtual disk to get a LUN; however, you do not end up with numerous volumes with non-meaningful names.
Specifying a previously created volume when using the StorageLink SR wizard to create an SR simplifies volume management and administration. In this situation, each VDI gets a LUN in the selected volume. However, you do not end up with excessive, potentially unmanageable numbers of volumes (that is, one for each VDI). Using this method enables you to create a high number of VDIs. You can also create a more user-friendly meaningful name for the volumes, rather than the auto-generated names. This method also provides more efficient storage because it enables you to use deduplication since virtual disk images that share common data, such as the same operating system or application, may be stored in the same volume.

Creating StorageLink SRs for NetApp Arrays

When StorageLink creates an SR (and the associated LUN and volume), StorageLink automatically creates the initiator group with the Linux operating system. Manually configuring initiator groups with other operating systems is not recommended.

To create a Fibre Channel SR using StorageLink, you should have an iSCSI license on the storage during the initial discovery phase of the NetApp storage controller or be running ONTAP 8.1. If neither one of these apply, create the SR by using the standard SR creation process (without StorageLink) as described in Creating a New SR.

Note: To use StorageLink to connect to a NetApp storage array, you must enable httpd on the storage array before using the XenCenter New SR wizard.

To create a StorageLink SR

Note: The XenCenter procedure for configuring Storagelink (Dell EqualLogic and NetApp) SRs shown below applies to servers running XenServer version 6.0 or higher.

To create an SR and a LUN for Fibre Channel with StorageLink