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COMP25212: COMP25212: Virtualization 3Virtualization 3
Subtitle: “What can we do to a VM?”
Learning Objectives:– To understand the VM-handling
mechanisms of a hypervisor
– To understand how many different value-added services are constructed on top of VM-handling mechanisms
COMP25212 1Feb 2013
Stopping a VMStopping a VM
Hypervisor stops and starts VM all the time:– to share CPUs– to serialize access to
resources
• Stop by:– Saving CPU registers
into Hypervisor data area
COMP25212 2
ApplicationsApplications
Guest AOperating System
Guest AOperating System
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
ApplicationsApplications
Host HardwareHost Hardware
Guest BOperating System
Guest BOperating System
Virtualized
Feb 2013
Starting a VMStarting a VM
• Hypervisor:– gains control (e.g.
clock tick)– saves previous VM’s
CPU registers– loads next VM’s
CPU registers– jumps to next VM’s
next-PC (in correct privilege state)
COMP25212 3
ApplicationsApplications
Guest AOperating System
Guest AOperating System
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
ApplicationsApplications
Host HardwareHost Hardware
Guest BOperating System
Guest BOperating System
Virtualized
Feb 2013
VM State While VM State While StoppedStopped
VM State:– Memory (all guest
physical memory)• includes Application
state, OS state
– CPU state (registers)– Small amount of I/O
state• Let’s stop VM when
I/O is quiescent!
COMP25212 4
ApplicationsApplications
Guest AOperating System
Guest AOperating System
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
ApplicationsApplications
Host HardwareHost Hardware
Guest BOperating System
Guest BOperating System
Virtualized
Feb 2013
““Freeze” a VMFreeze” a VM
• Once suspended, the VM image is self-contained– VM can be (e.g.)
copied to a file(LARGE file!)
• Now, what else can we do with this?
COMP25212 5
ApplicationsApplications
Guest AOperating System
Guest AOperating System
CPU registersCPU registers
I/O stateI/O state
Feb 2013
Move a VMMove a VM
COMP25212 6
ApplicationsApplications
Guest AOperating System
Guest AOperating System
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
ApplicationsApplications
Host Hardware XHost Hardware X
Guest BOperating System
Guest BOperating System
Virtualized
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
ApplicationsApplications
Guest COperating System
Guest COperating System
Virtualized
Host Hardware YHost Hardware Y
ApplicationsApplications
Guest BOperating System
Guest BOperating System
Feb 2013
Snapshot and Rollback Snapshot and Rollback a VMa VM
COMP25212 7
ApplicationsApplications
Guest AOperating System
Guest AOperating System
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
ApplicationsApplications
Host HardwareHost Hardware
Guest BOperating System
Guest BOperating System
Virtualized
Think: Optimizations?Feb 2013
ApplicationsApplications
Guest BOperating System
Guest BOperating System
Snapshot 1
ApplicationsApplications
Guest BOperating System
Guest BOperating System
…
Snapshot n
Archive a VMArchive a VM
COMP25212 8
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
Feb 2013
Rapid ProvisioningRapid Provisioning
COMP25212 9
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
ApplicationsApplications
Host HardwareHost Hardware
Guest COperating System
Guest COperating System
Virtualized
ApplicationsApplications
Guest BOperating System
Guest BOperating System
Feb 2013
Virtual AppliancesVirtual Appliances
• http://www.vmware.com/appliances/directory/
• over 1000 downloadable appliances
COMP25212 10
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
ApplicationsApplications
Guest BOperating System
Guest BOperating System
• e.g.:• mail server• web server• hotel system• virus scanner• firewall
Feb 2013
Deploying Secure Deploying Secure DesktopsDesktops
COMP25212 11
Virtual Machine Monitor/HypervisorVirtual Machine Monitor/Hypervisor
Host HardwareHost Hardware
Virtualized Desktop Machine
ApplicationsApplications
Guest Operating System
Guest Operating System
Feb 2013
Live MigrationLive Migration
• Optimizing live migration from “source” to “destination” VMM:– Copy every page from “source” to “destination” machine
• reset “dirty” bit in VMM’s page table for every page copied
– Repeat:• Find next non-“dirty” page in “source” machine• Copy to “destination” machine and reset “dirty” bit
– Until only minimal subset of pages left
– Suspend VM on “source”– Copy remaining pages to “destination”– Resume VM on “destination”
COMP25212 12Feb 2013
Load BalancingLoad Balancing
• Management software monitors “load” on all physical machines
• If loads are mismatched, migrate a VM from a loaded to a less-loaded machine
Independent of Application!
Independent of Operating System!
COMP25212 13Feb 2013
High AvailabilityHigh Availability
• For critical applications, keep a standby VM available on a different hardware system
• Regularly copy active VM image to standby VM (but don’t activate it)
• Activate standby VM if active VM stops responding (VM crashes? VMM crashes? Hardware system fails?)
Independent of Application!
Independent of Operating System!
COMP25212 14Feb 2013