From f6a38e543de9fbe96c24f3e867cdee9ef152f1f6 Mon Sep 17 00:00:00 2001 From: Mate Lakat Date: Tue, 9 Dec 2014 16:58:02 +0100 Subject: [PATCH] XenAPI: Cleanup introduction Remove references to XCP, remove driver domain specific information, update links to the latest (6.2) XenServer, add link to xenserver.org Change-Id: I5868f011e86c9368c2926344ac1ded5b230fc7e6 --- .../compute/section_introduction-to-xen.xml | 191 ++++++++---------- 1 file changed, 87 insertions(+), 104 deletions(-) diff --git a/doc/config-reference/compute/section_introduction-to-xen.xml b/doc/config-reference/compute/section_introduction-to-xen.xml index 24919ee5fa..7fa856ac35 100644 --- a/doc/config-reference/compute/section_introduction-to-xen.xml +++ b/doc/config-reference/compute/section_introduction-to-xen.xml @@ -5,8 +5,7 @@ version="5.0" xml:id="introduction-to-xen"> - Xen, XenAPI, XenServer, - and XCP + Xen, XenAPI, XenServer This section needs help This section is low quality, and contains out of date information. The Documentation Team is currently looking for individuals with @@ -14,113 +13,97 @@ Re-document Xen integration with OpenStack. - This section describes Xen, XenAPI, XenServer, and XCP, - their differences, and how to use them with OpenStack. After - you understand how the Xen and KVM architectures differ, you - can determine when to use each architecture in your OpenStack - cloud. + + This section describes XenAPI managed hypervisors, and how to + use them with OpenStack. +
- Xen terminology - Xen. A hypervisor that - provides the fundamental isolation between virtual - machines. Xen is open source (GPLv2) and is managed by - Xen.org, an cross-industry organization. - Xen is a component of many different products and - projects. The hypervisor itself is very similar across all - these projects, but the way that it is managed can be - different, which can cause confusion if you're not clear - which tool stack you are using. Make sure you know what - tool stack you want before you get started. - Xen Cloud Platform - (XCP). An open source (GPLv2) tool stack - for Xen. It is designed specifically as a platform for - enterprise and cloud computing, and is well integrated - with OpenStack. XCP is available both as a binary - distribution, installed from an iso, and from Linux - distributions, such as xcp-xapi in Ubuntu. The current versions of - XCP available in Linux distributions do not yet include - all the features available in the binary distribution of - XCP. - Citrix XenServer. A - commercial product. It is based on XCP, and exposes the - same tool stack and management API. As an analogy, think - of XenServer being based on XCP in the way that Red Hat - Enterprise Linux is based on Fedora. XenServer has a free - version (which is very similar to XCP) and paid-for - versions with additional features enabled. Citrix provides - support for XenServer, but as of July 2012, they do not - provide any support for XCP. For a comparison between - these products see the XCP Feature Matrix. - Both XenServer and XCP include Xen, Linux, and the - primary control daemon known as xapi. - The API shared between XCP and XenServer is called - XenAPI. OpenStack - usually refers to XenAPI, to indicate that the integration - works equally well on XCP and XenServer. Sometimes, a - careless person will refer to XenServer specifically, but - you can be reasonably confident that anything that works - on XenServer will also work on the latest version of XCP. - Read the XenAPI Object Model Overview for definitions - of XenAPI specific terms such as SR, VDI, VIF and - PIF. + Terminology +
+ Xen + + A hypervisor that provides the fundamental isolation between + virtual machines. Xen is open source (GPLv2) and is managed by + Xen.org, an cross-industry organization and a Linux + Foundation Collaborative project. + + + Xen is a component of many different products and projects. The + hypervisor itself is very similar across all these projects, + but the way that it is managed can be different, which can + cause confusion if you're not clear which toolstack you are + using. Make sure you know what toolstack you want before you + get started. + +
+
+ XenAPI + + XenAPI is one of the toolstacks that could control a Xen based + hypervisor. XenAPI's role is similar to libvirt's in the KVM + world. To learn more about XenAPI, visit the + + XenAPI Object Model Overview + + for definitions of XenAPI specific terms such as SR, VDI, VIF + and PIF. + + + OpenStack has a compute driver which talks to XenAPI, therefore + all XenAPI managed servers could be used with OpenStack. + +
+
+ XenServer + + An Open Source virtualization software which includes the Xen + hypervisor and XenAPI for the management. For more information + and product downloads, visit + + xenserver.org + . + +
Privileged and unprivileged domains - A Xen host runs a number of virtual machines, VMs, - or domains (the terms are synonymous on Xen). One of - these is in charge of running the rest of the system, - and is known as "domain 0," or "dom0." It is the first - domain to boot after Xen, and owns the storage and - networking hardware, the device drivers, and the - primary control software. Any other VM is - unprivileged, and are known as a "domU" or "guest". - All customer VMs are unprivileged of course, but you - should note that on Xen the OpenStack control software - (nova-compute) also runs in a domU. - This gives a level of security isolation between the - privileged system software and the OpenStack software - (much of which is customer-facing). This architecture - is described in more detail later. - There is an ongoing project to split domain 0 into - multiple privileged domains known as driver domains and - stub domains. - This would give even better separation between - critical components. This technology is what powers - Citrix XenClient RT, and is likely to be added into - XCP in the next few years. However, the current - architecture just has three levels of separation: - dom0, the OpenStack domU, and the completely - unprivileged customer VMs. + + A Xen host runs a number of virtual machines, VMs, or domains + (the terms are synonymous on Xen). One of these is in charge of + running the rest of the system, and is known as domain 0, or + dom0. It is the first domain to boot after Xen, and owns the + storage and networking hardware, the device drivers, and the + primary control software. Any other VM is unprivileged, and are + known as a domU or guest. All customer VMs are unprivileged, + but you should note that on Xen, the OpenStack Compute service + (nova-compute) + also runs in a domU. This gives a level of security isolation + between the privileged system software and the OpenStack + software (much of which is customer-facing). This architecture + is described in more detail later. +
- Paravirtualized versus hardware virtualized - domains - A Xen virtual machine can be paravirtualized (PV) or hardware virtualized (HVM). - This refers to the interaction between Xen, domain 0, - and the guest VM's kernel. PV guests are aware of the - fact that they are virtualized and will co-operate - with Xen and domain 0; this gives them better - performance characteristics. HVM guests are not aware - of their environment, and the hardware has to pretend - that they are running on an unvirtualized machine. HVM - guests do not need to - modify the guest operating system, which is essential - when running Windows. - In OpenStack, customer VMs may run in either PV or - HVM mode. However, the OpenStack domU (that's the one - running nova-compute) must be running in PV mode. + Paravirtualized versus hardware virtualized domains + + A Xen virtual machine can be paravirtualized (PV) or hardware + virtualized (HVM). This refers to the interaction between Xen, + domain 0, and the guest VM's kernel. PV guests are aware of + the fact that they are virtualized and will co-operate with Xen + and domain 0; this gives them better performance + characteristics. HVM guests are not aware of their environment, + and the hardware has to pretend that they are running on an + unvirtualized machine. HVM guests do not need to modify the + guest operating system, which is essential when running + Windows. + + + In OpenStack, customer VMs may run in either PV or HVM mode. + However, the OpenStack domU (that's the one running + nova-compute) must be + running in PV mode. +