Michael Lang
Xen Virtualization mwlang@cybrains.net
November 2008

The Main Players

Virtualization Awareness
Fully-virtualized
 All hardware fully emulated.
 Kernel is unaware it is virtualized.
Para-virtualized
 Kernel modified to be “aware”
 Direct access to some hardware
devices, so less emulation overhead.

CPU Technology: Intel-VT and AMD-V
What is it Good for?
 Efficient Hypervisor by eliminating
need to “trap and emulate”
End Result:
 Running an unmodified version of an
OS as a Guest.

When is Intel-VT and AMD-V Needed?
VMWare Xen
32-bit 64-bit 32-bit 64-bit 32-bit 64-bit 32-bit 64-bit
Intel-VT No Yes No Yes Yes Yes No No
AMD-V No No No No Yes Yes No No
Unmodified
Kernel Fully virtualized
Modified Kernel Para-virtualized

What am I getting into?
Why Use Virtual Technologies?

Implement High Availability
VM Guest stays up and running even if
the physical Host machine goes
down.
Requires:
 SAN
 Three or More Physical Hosts
 Clustered, Shared Filesystem

Increase Hardware Utilization
 Run More on Less.
 Boost CPU and RAM Utilization
dramatically.
 Take full advantage of RAM and
Multi-core CPU’s.

Separate Service from Hardware
 Liberate Windows Systems.
 Backup and Restore a Fully
configured system cheaply.
 Upgrade hardware painlessly.

Business Continuity
 Set up Once, distribute to multiple
Data Centers.
 Offsite Disaster Recovery through
simple backup/restore process.
 Load balance across Data Centers.

Try New Things
 Provision New Servers within an
Hour.
 Teardown/Rebuild of Servers is highly
efficient.
 Clone and perform “dry-runs” before
attempting on Production.

Getting Started…
Order of Importance:
 Sufficient RAM
 Fast Front-Side Bus (FSB)
 Fast Hard Drives and Controllers
 Multi-core CPU’s
 Cache memory
 CPU speed
 Network Bandwidth

Start Small…
 Take a Desktop, install 2gb of RAM.
 Install VMWare Server Free.
 Install Windows and Linux as guest
OS’s.
 Get to know the terminology.

Try it in the Data Center…
 Install Free versions of Xen or
VMWare Server on an underutilized
Server.
 Bring up your new Service on VM
Guests.
 Get comfortable managing.
 Learn to backup efficiently.

Make your Business Case…
 Show your boss, make your case, get
the equipment.
 Convert oldest, slowest or most
unstable servers first.
 Save critical resources and high I/O
systems (databases, file servers) for
last.
 Get used to diagnosing issues,
pinpointing bottlenecks or stability
issues.

Watch Your Performance Closely
Know when you’re saturating:
 Hard drive I/O throughput
 Network bandwidth
 CPU utilization
Commercial/Enterprise Licenses make
this easier to monitor and manage.

For High Availability
 Dedicated iSCSI VLAN w/dedicated
NICs.
 Line-speed, non-blocking switches
 Host Bus Adaptors with TCP/IP
offload Engines (TOE).
 Wide-striped LUN’s.
 Load-balancing Storage Processors on
your SAN

What I’m Using
Hardware Software
3 x Dell 2950’s Linux:
2 x quad-core Xeon 2.33ghz Oracle VM for Host
16-gb RAM
4x250gb RAID 5 SCSI Fedora Core 8, CentOS 4, CentOS
Dual port iSCSI HBA 5 Xen kernels for guests.
1 x Dell 2950 Red Hat’s Kickstart for
2 x quad-core Xeon 3.2ghz provisioning new VM guests.
16gb RAM
5x250gb RAID 5 SAS CentOS repositories to maintain
Dual port iSCSI HBA patches on Oracle VM Host and
CentOS guests.
1 x Dell AX150i
2 storage processors Fedora Core repositories for FC8
12x500gb SATA II drives
2 x Dell 6248 GbE Switches

Baphst01: xm list

Baphst01: xm top

What’s Running in our Environment?
Apache Servers
Host Guests
Rails Application Servers
Baphst01 18
Continuous Build Servers
Baphst02 10
DNS Servers
Baphst03 19
Email Servers
Baphst04 15
MySQL Servers
Total 62 PostgreSQL Servers
Subversion Server
Trac Wiki Servers
Repositories
Nagios

Maintenance Plan
 Whenever Guest Images are
provisioned or patched, Guest is
downed and image backed up to
SAN.
 We use automated deployment tools
and strict adherence to conventions
to configure guest VMs and deploy
our systems (Ruby on Rails).
 Stress Rebuild over Restore.

Maintenance Plan
 All config files kept in Subversion,
which is hot copied to SAN via SAMBA
shared resources.
 Mysql, Postgresql and SQL Server
2005 backed up to SAN via SAMBA
shared resources.
 SAN backed up to portable 500gb
USB drives via rsync.

Questions and Answers