live migration of virtual machines presented by: edward armstrong university of guelph
TRANSCRIPT
Live Migration of Virtual Machines
Presented by:Edward ArmstrongUniversity of Guelph
OverviewProblem DescriptionSolutionsStrengths and WeaknessesResults
Migrating an OS - Complexity
•Same machine.
•Hibernating a laptop.
Trivial
•Same Hardware, different Machine.
•Changing cluster nodes.
Moderate
•Different hardware.
Complex
Migrating an OS – Timescale
•Requires only long term storage to be migrated.
•Loses all process state information.
•Driver reloading solves hardware problems.
Reboot•Typically
performed on the same machine.
•Requires long term storage.
•Loses external connection information, ie. network status.
Hibernation
•Hibernation in short term storage (RAM).
•Typically used to maintain a low power state.
Suspend
•Processes are not implicitly frozen.
•Differences in hardware create problems.
•Solved by using virtual machines.
Live
ConsiderationsBoth machines must be active at
the same time.Migration of active live services.Total migration time.Resource contention.
Migrating memory
Push
PausePull
Memory - Pure stop and copy.
Pros◦ Simplicity.◦ Consistency.
Cons◦ Downtime proportional to
memory.◦ Unacceptable for live services.
Push
PausePull
Source Machine Target Machine
Memory - On demand migration.
Pros◦ Shorter downtime.◦ Consistency.
Cons◦ Longer migration time.
Push
PausePull
Target MachineSource Machine
Page fault request
Send page
Memory - Pre copy migration.
Pros◦ Copy low fault pages quickly.◦ Works well for live processes.
Cons◦ Large number of faults for
busy memory.
Push
PausePull
Target MachineSource Machine
Live page fault
Iterative push
Network and disk resources.Unique to an OS instance.Ordering of resources are non-
determinsitic.Need to maintain open network
connections.
Resolving network connections with an ARP* response.
Source MachineNo Address
Target Machine192.168.0.102
LAN
*ARP: Address Resolution Protocol
Packets
Resolving network connections with an ARP* response.
Source MachineNo Address
Target Machine192.168.0.102
LAN
*ARP: Address Resolution Protocol
Unsolicited ARP reply
Packets
Resolving network connections with an ARP* response.
Source Machine192.168.0.102
Target MachineNo Address
LAN
*ARP: Address Resolution Protocol
Packets
Network resources.Pros
◦Handled by external devices.◦Similar scheme can be used to
migrate disk services (not covered in paper).
Cons◦Small amount of packet loss.◦Requires a LAN with unsolicited ARP
responses enabled.
Design Overview
Pre-Migration
Reservation Pre-Copy
Stop and CopyCommitActivate
Source Machine Target Machine
Select a new target machine
Design Overview
Pre-Migration
Reservation Pre-Copy
Stop and CopyCommitActivate
Source Machine Target Machine
Confirm available resources on target.Failure means VM continues to run on source.
Design Overview
Pre-Migration
Reservation Pre-Copy
Stop and CopyCommitActivate
Source Machine Target Machine
Transfer memory.Retransmit memory used during transfer.
Design Overview
Pre-Migration
Reservation Pre-Copy
Stop and CopyCommitActivate
Source Machine Target Machine
Halt source to redirect network trafficand transfer CPU state.
Design Overview
Pre-Migration
Reservation Pre-Copy
Stop and CopyCommitActivate
Source Machine Target Machine
Verify transfer complete.Disable source.
Design Overview
Pre-Migration
Reservation Pre-Copy
Stop and CopyCommitActivate
Source MachineTarget Machine
Activate target machine
Summary of DesignAt all times there is at least one
consistent image available.Minimized down time.Not a fast process overall.Requires tuning.Requires certain hardware.
Performance – Dirty Pages.
8 second granularity, used to decide which pages make for good pre-migration.
Performance
Performance
1- 4 pre-copy iterations
Performance
1- 4 pre-copy iterations
Performance
1- 4 pre-copy iterations
Thank You