A data center is a facility used to house computer systems and associated components, such as telecommunications and storage systems. It generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (e.g., air conditioning, fire suppression) and various security devices. Large data centers are industrial scale operations using as much electricity as a small townand sometimes are a significant source of air pollution in the form of diesel exhaust.
A Virtual Data Center (VDC) is an on demand configurable pool of shared computing resources allocated within a public cloud environment, providing certain level of isolation between the different organizations (denoted as users hereafter) using the resources. The isolation between one VDC user and all other users of the same cloud (other VDC users as well as other public cloud users) is achieved normally through allocation of a Private IP Subnet and a virtual communication construct (such as a VLAN or a set of encrypted communication channels) per user. In a VDC solution, the previously described mechanism, providing isolation within the cloud, is accompanied with a VDC function (again, allocated per VDC user) that secures, by means of authentication and encryption, the remote access of the organization to its VDC cloud resources. With the introduction of the described isolation levels, an organization using this service is in effect working on a ‘virtually private’ cloud (i.e. as if the cloud infrastructure is not shared with other organizations), and hence the name VDC.
VDC is most commonly used in the context of cloud infrastructure services (IaaS). In this context, the infrastructure provider, providing the underlining public cloud infrastructure, and the provider realizing the VDC service over this infrastructure, may be different vendors.
Data stores are virtual representations of combinations of underlying physical storage resources in the datacenter. These physical storage resources can come from the following sources:
- Local SCSI, SAS, or SATA disks of the server
- Fiber Channel SAN disk arrays
- iSCSI SAN disk arrays
- Network Attached Storage (NAS) arrays
Networks in the virtual environment connect virtual machines to one another and to the physical network outside of the virtual datacenter
Virtual machines can be designated to a particular host, cluster or resource pool, and a data store when they are created. After they are powered-on, virtual machines consume resources dynamically as the workload increases or give back resources dynamically as the workload decreases.
Provisioning of virtual machines is much faster and easier than physical machines. New virtual machines can be created in seconds. When a virtual machine is provisioned, the appropriate operating system and applications can be installed unaltered on the virtual machine to handle a particular workload as though they were being installed on a physical machine. A virtual machine can be provisioned with the operating system and applications installed and configured.
Resources get provisioned to virtual machines based on the policies that are set by the system administrator who owns the resources. The policies can reserve a set of resources for a particular virtual machine to guarantee its performance. The policies can also prioritize and set a variable portion of the total resources to each virtual machine. A virtual machine is prevented from being powered-on and consuming resources if doing so violates the resource allocation policies.