Scaling Xen within Rackspace Cloud Servers

Scaling Xen within
Rackspace Cloud Servers

Chris Behrens
chris.behrens@rackspace.com

XenSummit 2012, San Diego, CA USA
August 28, 2012

1

Agenda
•  Intro to Rackspace Cloud Servers
•  Why Xen?
•  Xen to XenServer
•  OpenStack Basics
•  OpenStack at Rackspace
•  Scaling OpenStack Deployment
•  Future

RACKSPACE® HOSTING | WWW.RACKSPACE.COM
2

Intro to Cloud Servers

3

Overview

•  Public Cloud product under Rackspace’s Open Cloud portfolio
•  First Gen
–  Code originated from Slicehost acquisition
–  Initially Xen 3.x, but migrated to XenServer
•  Next Gen
–  Public Launch 8/1/2012
–  Powered by OpenStack
•  XenServer 6
•  Linux, Windows, and FreeBSD VMs

4

Statistics

•  180,000+ total Rackspace customers (not just Cloud Servers)
•  Tens of thousands of hosts
•  Hundreds of thousands of VMs
•  Millions of snapshots

5

Why Xen?

6

Why Xen?

•  Thin hypervisor layer
•  Open source
•  Excellent driver support due to Linux dom0
•  Good API
•  Good performance
•  Along with Linux, Windows VMs are a must
–  Same virtualization technology desired for Windows
–  Microsoft will support
–  Good PV driver support

7

Xen to XenServer

8

Xen to XenServer
Cloud Servers use of Xen

•  LVM
–  Logical volumes per VM
•  Base images stored as tar files
•  Kernel and ramdisk outside of images
•  Shell out to run ‘xm’ commands
•  Snapshots w/ LVM
–  Mounted and contents rsynced to another host
•  No agent
–  Modifications inside images done via mounting powered off VM

9

Xen to XenServer
Xen to XenServer changes

•  VHDs for virtual disk images
–  Tarred and gzipped
•  Kernel and ramdisk inside images
•  Snapshots via XenAPI
–  Whole VDI chain wrapped in OVF container for upload to glance
•  Agent inside VM images
–  Communication via Xenstore
–  File injection, password resets, networking setup

10

Xen to XenServer
Migrating

•  Pick a XenServer host
•  Create VDI
•  Attach VDI to dom0
•  Partition, mkfs, and mount the new virtual disk
•  LVM Snapshot original Xen VM and mount it
•  rsync snapshot contents to mounted VDI on new host
•  Power off original Xen VM and mount its virtual disk
•  rsync again to new host to catch changes since snapshotting
•  Extract a tar file into mounted VDI containing kernel, ramdisk, agent
•  Unmount and detach VDI from dom0
•  Create new VM record and attach VDI
•  Start the new VM

11

OpenStack
The Basics

12

OpenStack
Components

•  Nova
–  Compute controller with various hypervisor drivers
•  Glance
–  VM Image registry
•  Swift
–  Object storage
•  Quantum/Melange
–  Networking
•  Cinder
–  Volumes/Block storage
•  Keystone
–  Authentication
–  Authorization
–  API Endpoint discovery

13

OpenStack
Typical OpenStack Deployment

keystone

nova glance

nova-api glance-api glance-registry
RabbitMQ

MySQL
nova-scheduler
MySQL
nova-network

nova-compute swift

14

OpenStack
nova-compute w/ XenAPI

•  Runs in a utility domU on each host
•  Images downloaded in dom0 Physical host running XenServer"
–  glance XenAPI plugin
•  Images attached to nova-compute dom0" nova utility domU"
domU
–  Partitioning changes glance plugin nova-compute
–  file-system resizing
agent plugin
•  Monitors VMs’ power_state
•  Snapshots/backups xenstore plugin nova instance
•  VM resize/migration domUs
–  rsync to new host
•  Communicates w/ agent inside VMs
–  Via xenstore

15

OpenStack
XenAPI VM Calls

•  VM.start / VM.start_on •  VM.add_to_VCPUs_params
•  VM.destroy •  VM.get_VBDs
•  VM.clean_reboot •  VM.get_record
•  VM.hard_reboot •  VM.get_by_uuid
•  VM.clean_shutdown •  VM.get_by_name_label
•  VM.hard_shutdown •  VM.set_name_label
•  VM.pause •  VM.add_to_xenstore_data
•  VM.unpause •  VM.remove_from_xenstore_data
•  VM.suspend •  VM.assert_can_migrate
•  VM.resume •  VM.migrate_send
•  VM.snapshot •  VM.pool_migrate

16

OpenStack
Rackspace Specifics

17

OpenStack Rackspace Specifics
Source Code

•  Rackspace tracks trunk
–  Deployed code generally less than 2 weeks behind trunk
•  Some custom patches on top of trunk
–  Features specific to Rackspace
–  Custom scheduling to meet Rackspace needs
–  Scaling with OpenStack Compute Cells

18

OpenStack Compute Cells

•  Scaling beyond small nova deployments
–  Effectively ties multiple nova deployments together
•  Developed by Rackspace
•  Targeted for Grizzly OpenStack release
•  Hierarchical tree
–  Multiple parents supported
•  API cell(s) at top of the tree
•  Compute cell(s) underneath
•  DB and RabbitMQ per cell
•  Scalability
–  Splits connections to DB and RabbitMQ
–  Less work to schedule new VM placement

19

OpenStack Nova Multi-cell Diagram
API Cell

RabbitMQ

MySQL
nova-api

nova-cells

Compute Cell 1" Compute Cell 2"

nova-cells nova-cells

RabbitMQ
RabbitMQ

MySQL
MySQL

nova-scheduler nova-scheduler

nova-network nova-network

nova-compute nova-compute

20

Deploying OpenStack

21

Deploying OpenStack
‘Inception’

•  Private internal cloud
–  Based on Openstack, called iNova
–  OpenStack services for public cloud run virtualized under iNova
•  Easy to spin up additional services for load balancing
–  Enables quick reaction to load spikes
•  Easier deployments of new compute cells
•  Automated reaction to downed hosts
•  Enables new strategies for deployments
–  Replace vs Upgrade

22

Deploying OpenStack
iNova Diagram

iNova"
OpenStack Control
Public Cloud
Infrastructure for
XenServer
Public Cloud"
hosts
XenServer hosts"

domUs

XenServer host w/ Public Cloud
OpenStack Control
Infrastructure for iNova" XenServer
hosts

23

Deploying OpenStack
Continuous Deployment

•  Trunk and custom branches merged multiple times daily
–  Unit Tested and Packaged
•  Configuration managed with puppet
–  Follows same QE and Continuous Deployment rules as code
•  QE Environment
–  OpenStack control infrastructure deployed on iNova
–  nova-compute upgraded on 200 hosts
–  Smoke tests
•  Staging Deploy
–  Uses the same packages and puppet manifests

24

Future

25

Future
Improvements desired from Xen

•  Better VM resource isolation
–  I/O scheduling weights per virtual disk
•  Built in live migration without shared storage
•  More information about VM resource usage
–  Disk usage
–  Help us improve OpenStack code
–  Help customers react to bad situations
•  XenAPI call to write to live xenstore
•  Improve XenServer upgrade experience

26

Future
Rackspace’s Other Interests

•  Better VDI introduction for new VMs
–  Look at VDI.introduce vs mv’ing VDIs and doing an sr-scan
•  Incremental backups
–  Delta VHDs instead of all VHDs
•  Updated plugins using python >= 2.6
–  Cleans up workarounds for no built-in ‘uuid’ module
–  Allows use of newer python features like context managers
•  Better continuous deployment and testing
–  Virtualize all of OpenStack
•  Requires spinning XenServer on XenServer
•  Wipe out compute nodes for QE environment
•  Enable virtual labs for OpenStack developers
–  Puppet used to configure XenServer

27

Future
iNova with Dev/QE Environments

OpenStack QE
iNova" Environment"

OpenStack
XenServer
Control
‘hosts’
Infrastructure

XenServer hosts"
OpenStack Dev
Environment"

domUs
OpenStack
XenServer
Control
‘hosts’
Infrastructure
XenServer host w/
OpenStack Control
Infrastructure for iNova"

28

"
Chris Behrens"
chris.behrens@rackspace.com"

RACKSPACE® HOSTING | 5000 WALZEM ROAD | SAN ANTONIO, TX 78218
US SALES: 1-800-961-2888 | US SUPPORT: 1-800-961-4454 | WWW.RACKSPACE.COM

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29

Scaling Xen within Rackspace Cloud Servers

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