Citrix Systems 4.2 manual About Secondary Storage, About Physical Networks

Chapter 3. Cloud Infrastructure Concepts

•Dell EqualLogic™ for iSCSI

•Network Appliances filers for NFS and iSCSI

•Scale Computing for NFS

If you intend to use only local disk for your installation, you can skip adding separate primary storage.

3.7. About Secondary Storage

Secondary storage stores the following:

•Templates — OS images that can be used to boot VMs and can include additional configuration information, such as installed applications

•ISO images — disc images containing data or bootable media for operating systems

•Disk volume snapshots — saved copies of VM data which can be used for data recovery or to create new templates

The items in secondary storage are available to all hosts in the scope of the secondary storage, which may be defined as per zone or per region.

CloudPlatform manages the allocation of guest virtual disks to particular primary storage devices.

To make items in secondary storage available to all hosts throughout the cloud, you can add object storage in addition to the zone-based NFS Secondary Staging Store. It is not necessary to copy templates and snapshots from one zone to another, as would be required when using zone NFS alone. Everything is available everywhere.

Object storage is provided through third-party software such as Amazon Simple Storage Service (S3) or any other object storage that supports the S3 interface. Additional third party object storages can be integrated with CloudPlatform by writing plugin software that uses the object storage plugin capability.

CloudPlatform provides some plugins which we have already written for you using this storage plugin capability. The provided plugins are for OpenStack Object Storage (Swift, swift.openstack.org1) and Amazon Simple Storage Service (S3) object storage. The S3 plugin can be used for any object storage that supports the Amazon S3 interface. When using one of these storage plugins, you configure Swift or S3 storage for the entire CloudPlatform, then set up the NFS Secondary Staging Store for each zone. The NFS storage in each zone acts as a staging area through which all templates and other secondary storage data pass before being forwarded to Swift or S3. The backing object storage acts as a cloud-wide resource, making templates and other data available to any zone in the cloud.

There is no hierarchy in the Swift storage, just one Swift container per storage object. Any secondary storage in the whole cloud can pull a container from Swift at need.

3.8. About Physical Networks

Part of adding a zone is setting up the physical network. One or (in an advanced zone) more physical networks can be associated with each zone. The network corresponds to a NIC on the hypervisor host. Each physical network can carry one or more types of network traffic. The choices of traffic

1http://swift.openstack.org

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