nova: virtapi

在nova中virtapi的定義放在/usr/share/pyshared/nova/virt/virtapi.py當中，只是用來制定api的spec

Nova: Xenserver Block Migration support on OpenStack

 Block migration  --- Xenserver必須支援Storage XenMotion的feature才可以使用此功能

Prerequisites 

• Compatible XenServer hypervisors. The hypervisors must support the Storage XenMotion feature. Please refer to the manual of your XenServer to make sure your edition has this feature.

	Note
	Please note, that you need to use an extra option --block-migrate for the live migration command, in order to use block migration.

	Note
	Please note, that block migration works only with EXT local storage SRs, and the server should not have any volumes attached.

OpenStack Security Group設定

為了讓Security Group的相關設定都交給Quantum Service來代理(proxy)處理，所以必須在/etc/nova/nova.conf中做以下的設定，以避免與原來Nova Networking所處理的Security Group相衝突。



## security groups ##
firewall_driver = nova.virt.firewall.NoopFirewallDriver
security_group_api = quantum

OpenStack: nova.conf section

 Sections

Configuration options are grouped by section. The Compute config file supports the following sections.

[DEFAULT]

Almost all of the configuration options are organized into this section. If the documentation for a configuration option does not specify its section, assume that it should be placed in this one.

[cells]

The cells section is used for options for configuring cells functionality. See the Cells section of the OpenStack Compute Admin Manual for more details.

[baremetal]

This section is used for options that relate to the baremetal hypervisor driver.

[conductor]

The conductor section is used for options for configuring the nova-conductor service.

[trusted_computing]

The trusted_computing section is used for options that relate to the trusted computing pools functionality. Options in this section describe how to connect to a remote attestation service.

Nova Conductor Service: no-db-compute for compute node

Q: 為何要做nova conductor service?這個從folsom版本開始討論構思，一直到了grizzly版本才合併。nova conductor究竟是啥樣子的服務呢!!?

[Dev List]
     Nova Conductor Dev List, http://lists.openstack.org/pipermail/openstack-dev/2012-November/002573.html

A:
主要是不透過Nova DB的存取來降低效能的瓶頸以及compromised compute node會帶來淺在的危險。

 The nova-conductor service is key to completing no-db-compute. Conceptually, it implements a new layer on top of nova-compute.



[Objective]
1. Compute nodes are the least trusted part of a nova deployment, so removing direct database access is a step toward reducing the potential impact of a compromised compute node.

2. The other benefit of no-db-compute is for upgrades. Direct database access complicates the ability to do live rolling upgrades

Reference:

1. http://cloudystuffhappens.blogspot.tw/2013/04/understanding-nova-conductor-in.html
2. http://russellbryantnet.wordpress.com/2013/02/19/deployment-considerations-for-nova-conductor-service-in-openstack-grizzly/

Nova rootwrap

使用root wrapper可以让非特权用户以root身份尽可能安全地执行部分操作。nova曾经使用sudoers文件来列出允许执行的特权命令，使用sudo来运行这么命令，但是这样不容易维护，而且不能进行复杂的参数处理，rootwrap就是为了解决这些问题。

使用sudo nova-rootwrap config-file command，而不再是使用sudo command。只需要使用一个通用的sudoers使nova-rootwrap以root身份运行。nova-rootwrap查看配置文件，加载command filters，检查请求的命令是否匹配某个filter，如果匹配就以root身份运行，否则就拒绝请求。

Reference:

1. http://my.oschina.net/chape/blog/119990

2. https://wiki.openstack.org/wiki/Nova/Rootwrap#How_rootwrap_works

OpenStack Nova: nova.conf 中的flag

https://github.com/openstack/nova/blob/stable/folsom/nova/flags.py

Nova Networking Design Mode

Type	Strengths	Weaknesses
Flat	Extremely simple. No DHCP broadcasts.	Requires file injection into the instance. Limited to certain distributions of Linux. Difficult to configure and is not recommended.
FlatDHCP	Relatively simple to setup. Standard networking. Works with all operating systems.	Requires its own DHCP broadcast domain.
VlanManager	Each tenant is isolated to their own VLANs.	More complex to set up. Requires its own DHCP broadcast domain. Requires many VLANs to be trunked onto a single port. Standard VLAN number limitation. Switches must support 802.1q VLAN tagging.
FlatDHCP Multi-host HA	Networking failure is isolated to the VMs running on the hypervisor affected. DHCP traffic can be isolated within an individual host. Network traffic is distributed to the compute nodes.	More complex to set up. By default, compute nodes need public IP addresses. Options must be carefully configured for live migration to work with networking.

nova-api

Ubuntu OpenStack Grizzly verison

nova-api - OpenStack Compute - API frontend
nova-api-ec2 - OpenStack Compute - EC2 API frontend
nova-api-metadata - OpenStack Compute - metadata API frontend
nova-api-os-compute - OpenStack Compute - OpenStack Compute API frontend
nova-api-os-volume - OpenStack Compute - OpenStack Volume API frontend

nova-api 和 nova-api-os-compute 、nova-api-os-volume 有不一樣嗎?!

用apt-get source nova-api nova-api-os-compute nova-api-os-volume來看他們的sha1sum似乎都是一樣的。

root@SAMEVEDStack:[~/openstack_ubuntu_src]$ sha1sum */*debian.tar.gz
af5e49592dd634915d3c20883e326ef8caf23929  nova-api/nova_2012.1.3+stable-20120827-4d2a4afe-0ubuntu1.4.debian.tar.gz
af5e49592dd634915d3c20883e326ef8caf23929  nova-api-os-compute/nova_2012.1.3+stable-20120827-4d2a4afe-0ubuntu1.4.debian.tar.gz
af5e49592dd634915d3c20883e326ef8caf23929  nova-api-os-volume/nova_2012.1.3+stable-20120827-4d2a4afe-0ubuntu1.4.debian.tar.gz

root@SAMEVEDStack:[~/openstack_ubuntu_src]$ sha1sum */*orig.tar.gz

aefedbf9e98d9c104a2293c9f9a18e95f3cabd0f  nova-api/nova_2012.1.3+stable-20120827-4d2a4afe.orig.tar.gz

aefedbf9e98d9c104a2293c9f9a18e95f3cabd0f  nova-api-os-compute/nova_2012.1.3+stable-20120827-4d2a4afe.orig.tar.gz

aefedbf9e98d9c104a2293c9f9a18e95f3cabd0f  nova-api-os-volume/nova_2012.1.3+stable-20120827-4d2a4afe.orig.tar.gz

root@SAMEVEDStack:[~/openstack_ubuntu_src]$ sha1sum */*dsc

08250fdc4e761f4dc62d32f734ef7646ece27d2d  nova-api/nova_2012.1.3+stable-20120827-4d2a4afe-0ubuntu1.4.dsc

08250fdc4e761f4dc62d32f734ef7646ece27d2d  nova-api-os-compute/nova_2012.1.3+stable-20120827-4d2a4afe-0ubuntu1.4.dsc

08250fdc4e761f4dc62d32f734ef7646ece27d2d  nova-api-os-volume/nova_2012.1.3+stable-20120827-4d2a4afe-0ubuntu1.4.dsc

Host Aggregate : 用來在availability zone中進行劃分

Host aggregates are a mechanism to further partition an availability zone; while availability zones are visible to users, host aggregates are only visible to administrators. 

[Note]

Each node can have multiple aggregates, each aggregate can have multiple key-value pairs, and the same key-value pair can be assigned to multiple aggregate.

Xenserver

當使用Xenserver當作hypervisor時，可以使用host-aggregate來管理Xenserver Resource Pool以支援Live migration。

nova flavor

所謂的"flavor"就是指VM Instance Type

nova flavor-list可以看出