1. High Availability through Virtualization
Is RAID enough?
Tomas Florian

2. Florien Consulting Linux servers Windows workstation interoperability
VPNs / Remote access
.NET development

3. Summary High Availability Virtualization HA + Virtualization Questions
DRBD
Failover
Heartbeat
Virtualization
Xen vs VMWare
Xen architecture
HA + Virtualization
Questions

4. High Availability : HA Linux-ha.org project Graceful degradation
Better than:

5. Challenges Replicate data Failover Automatically detect failure
node1
node2
Replicate data
DRBD Network RAID-1
Failover
Take over responsibilities from the dead peers
Automatically detect failure
Heartbeat

6. Replicate Data: DRBD Distributed Replicated Block Device
Network RAID-1
One active drive (primary)
N spare drives replicated on the network in real-time
In case of primary HD failure, switch to one of the available secondary drives
Mount just like any other block device mount /dev/drbd0 /data

7. Failover : haresources
node1 running Apache
node2 running qmail
node1 dies … apache dies. Node 2:
Take over primary use of DRBD device
Take over IP
Take over Apache

8. Detect Failure: heartbeat
Ping through ethernet
Split brain
Ping through serial cable + ethernet
STONITH – Shoot The Other Node In The Head
.. node2 is dead .. Time to takeover
.. node1 is dead .. Time to takeover
node1
node2

9. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2
Active resources
Backup resources

10. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2
Active resources
Backup resources
Dead resources

11. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2
Active resources
Backup resources
Dead resources

12. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2
Active resources
Backup resources
Dead resources

13. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2
Active resources
Backup resources
Dead resources

14. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2
Active resources
Backup resources
Dead resources

15. Example Apache qmail drbd0 drbd1 drbd0 drbd1 node1 node2
Active resources
Backup resources
Dead resources

16. Example drbd0 drbd1 drbd0 drbd1 node1 node2 Active resources
Apache
Named
mysql
qmail
drbd0
drbd1
drbd0
drbd1
node1
node2
Active resources
Backup resources

17. Summary High Availability Virtualization HA + Virtualization Questions
DRBD
Failover
Heartbeat
Virtualization
Xen vs VMWare
Xen architecture
HA + Virtualization
Questions

18. Xen Pronounced ‘Zen’ Open Source
Run multiple virtual machines on one physical machine
Like VMWare but different (better)

19. Xen Architecture

20. Setting up Xen Install xen software on any Linux Patch Domain-0 kernel
Boot to the new Domain-0 kernel
Deploy Domain-U virtual machines
Allocate disk
Deploy any distribution with a patched Domain-U kernel
…Or use a distribution that does this for you

21. Full Virtualization vs Paravirtualization
Needs kernel patch
Open source guest OS only (MS will not let you patch Windows kernel)
Full virtualization
Hypervisor implemented with VT CPUs
Windows on Xen possible

22. VT hardware Intel AMD Check that your BIOS also supports VT
Vanderpool technology
Intel Pentium D
Intel Core Duo
AMD
Pacifica
Check that your BIOS also supports VT

23. VT support in Xen 2.0.7 stable as a rock (but no VT)
3.0.2 unstable (VT… almost)
People regularly report success running Windows guests …
… and crashes
Once v3 becomes stable it will be unstoppable

24. Summary High Availability Virtualization HA + Virtualization Questions
DRBD
Failover
Heartbeat
Virtualization
Xen vs VMWare
Xen architecture
HA + Virtualization
Questions

25. No virtualization… MySQL samba named Apache qmail drbd0 drbd1 drbd0
node1
node2
Active resources
Backup resources

26. …with virtualization Web server Mail server drbd0 drbd1 drbd0 drbd1
Apache
qmail
MySQL
named
named
drbd0
drbd1
drbd0
drbd1
node1
node2
Active resources
Backup resources

27. Gains Whole filesystem protection Simplified management Security:
/ … not just /data
Simplified management
Manage failover for few machines rather than tens of services
No complicated syncing of updates or configuration on the nodes
Security:
If one service is hacked, only one VM is compromised

28. Pit falls Performance Watch out for: Don’t forget to backup
Running VMs more resource intensive than running daemons
Watch out for:
Virtual Memory thrashing
DRBD sync speed
HD performance
… going overboard
Don’t forget to backup

29. Resources Linux High Availability Project Xen web site
Linux-ha.org
Xen web site
Google search for “xen”
Xen Distributions
SuSE
FC5
Xen Live CD
… or just compile on any 2.4.x x kernel
Paid support

30. Summary High Availability Virtualization HA + Virtualization Questions
DRBD
Failover
Heartbeat
Virtualization
Xen vs VMWare
Xen architecture
HA + Virtualization
Questions

31. Questions