xcp的全稱是， xen cloud platfom, 從名字上看，這些軟件都和xen有關係，實際上也如此．
這些都是虛擬化的相關產品．xen是一個Hypervisor, 所謂的vmm(virtual machine manager)管理程序，是硬件虛擬化的衆多技術之一，其目的就是爲了讓多個操作系統同時運行在一臺主機設備．我們可以將上面描述的環境(架構)叫做雲計算中的iaas. 可以使共有云,或者私有云.
Robert P. Goldberg 將Hypervisor分爲2種類型:
type1: 例如有Citrix XenServer, VMware ESX/ESXi, and Microsoft Hyper-V (vm運行在硬件上的第二層)
type2: KVM and VirtualBox are examples of Type 2 hypervisors. 這裏我認爲vmware workstation, fusion 也應該屬於type2. (vm運行在硬件上的第三層)
至於xen我認爲也應該屬於type1, 因爲xen server 和 xcp都是基於xen衍生過來, 而 xen僅僅是一個簡單的Hypervisor, 而 citrix xen server , xcp 是一個hypervisor + api + tools 的套裝.
下面是網友針對xen,xenserver,xcp的一些總結,非常精闢和準確.
said by Scott Alan Miller on community.spiceworks
http://community.spiceworks.com/topic/131849-xen-vs-xenserver-vs-xcp
Xen: The open source, completely free granddaddy of the Xen family (which at one time had many children, most of whom are now gone.) Xen is different from all of its competitors in that it is a hypervisor ONLY and not a virtualization ecosystem (no management console, no extra features, no nothing.) It’s just a tiny little hypervisor. This is confusing because we lump Xen with HyperV, for example, but it is not an apples to apples comparison. Xen is like the hypervisor inside HyperV that no one even knows the name of.
XenServer: The primary commercial virtualization suite built on technologies derived from Xen. XenServer is an “older” version of Xen with some features removed and other featurs hidden behind “add ons.” So XenServer is far less functional than Xen and is not completely free (it can be, but many features are not.) XenServer is a full suite with all of the nice console and tools, APIs, etc. Much more user friendly than Xen and requires no core OS knowledge to get it working unlike Xen that requires you to really know the Dom0 environment well.
XCP: Xen Cloud Platform. XCP is a full virtualization suite based on Xen. It uses real Xen and combines in all of the other components needed to be a full suite just like XenServer, vSphere and HyperV. It is open source and comes from the Xen people. Today, when people talk about Xen, they mostly talk about XCP as XCP is the apple to apple with the other products and not just the hypervisor. You lose no functionality going with XCP over Xen on its own but it is far easier. XCP is designed to be interoperable with most, if not all, APIs from XenServer so that they can share tools giving XCP a lot of important options.