This document discusses challenges related to virtual machine (VM) migration in cloud computing. It provides background on cloud computing and virtual machines. Key issues discussed include automated service provisioning, VM migration for server consolidation and energy management, and security challenges. The document also covers motivation for VM migration when workload increases trigger resource requirement changes. Methods for VM migration discussed include memory, network, and device migration techniques. Performance evaluation results of migration are presented. Migration across data centers introduces additional challenges like increased latency. Proposed solutions discussed encryption for security and redirection approaches to handle increased latency.

1. Challenges in Cloud Computing – VM
Migration
Sarmad Makhdoom
2012-03-0019
Kamran Khalil
2012-03-0012
Hafeez ur Rehman
2012-03-0031

2. Introduction

3. Cloud Computing
•
Cloud computing is an umbrella term used to refer to Internet based
development and services
•
A number of characteristics define cloud data, applications services and
infrastructure:
▫
▫
▫
Remotely hosted: Services or data are hosted on remote infrastructure.
Ubiquitous: Services or data are available anywhere.
Commodified: The result is a utility computing model similar to traditional
that of traditional utilities, like gas and electricity - you pay for what you
would want!

4. Virtual Machines
• A virtual machine provides interface identical to underlying bare
hardware
▫ i.e. all devices, interrupts, memory, page tables etc.
• Applications of Virtual Machines
• Virtualization Software
▫
▫
▫
▫
VMWare
ZAP
Xen
QEMU

5. Virtual Machines in Cloud
▫ Benefits of Virtual Machines






Virtualization help making efficient use of hardware resources
Facilitates a greater degree of abstraction
Easily move from one piece of hardware to another
Replicate them at will
Create more scalable and flexible infrastructure
Snapshots
▫ Cloud computing has taken that degree of efficiency and agility realized
from virtualization
 Pooled resources
 Geographic diversity
 Universal connectivity

6. Research Problems

7. Research Problems
• Automated services provisioning
• Virtual machine migration
•
•
•
•
•
•
•
Server consolidation
Energy management
Traffic management and analysis
Data security
Software frameworks
Storage technology and data management
Novel cloud architecture

8. Motivation

9. Motivation
• Consider a data center consisting of “n” physical machines (PM) hosting
“m” VMs implementing one customer application each
• Resources(CPU, Network, Memory, I/O) are allocated to each VM to
handle the workload and operate at certain performance level (SLA)
• Each VM sees workload fluctuation from time to time => resource
requirement changes
# of user visit increases
PM Capacity
VM1
VM2
cricinfo
Network Bandwidth
Memory
CPU
mail server
Virtualization Layer
Hardware
Resource
Allocation
VM1
N = 5Gbps
M = 8GB
C = 4 cores
= 10 Gbps
= 16 GB
= 8 cores
VM2
N = 5Gbps
M = 8GB
C = 4 cores

10. Motivation
• An increase in workload can be handled by allocating more resources to
it, if idle resources are available
• Main Issues:
▫ What if PM does not have (enough or no) idle resources to satisfy VM's
requirement?
 Performance of the application degrades
 SLA violation occurs
• Key Ideas
▫ Replication VMs
▫ Migrating VMs

11. Virtual Machine Migration
It is impossible or impractical to bring the data (or devices) close to the computation
engines.

12. Virtual Machine Migration
• Why we need migration?
• When we need to migrate?
• How migration is done?
• Issues in long distance migration (across data centers)

13. When we need to migrate? [NSDI’ 07]
• Hotspots can cause SLA violations
▫ Burden on some Virtual or Physical Machines are called hotspots
• Hotspot Detection (Sandpiper)
▫ Black-box Monitoring
 CPU (/proc)
 Network (/proc/net/dev)
 Memory (swap)
▫ Gray-box Monitoring
 Gather OS level statistics and application logs
• A hotspot is flagged only if thresholds or SLAs are exceeded for a
sustained time
Wood T et al (2007) Black-box and gray-box strategies for virtual machine migration. In: Proc of NSDI

14. Gathering
resource usage
statistics
Gathers on that
server
processor, network
Determine:
What virtual servers should migrate
Monitors usage profiles to detect
Where to move them
hotspots.
Construct resource much any resource exceeds a the
How
Hotspot: of a resource to allocate
usage profiles forvirtual servers afterviolation) for a sustain
threshold(or SLA migration
each virtual server period
(Predict PM workload)
and memory swap
statistics
for each VM Implements a
daemon to gather
OS-level statistics
and application logs
Wood T et al (2007) Black-box and gray-box strategies for virtual machine migration. In: Proc of NSDI
14

15. When we need to migrate? [FGCS’ 12]
• SLA violation detection
▫ Mapping low-level resource metrics to high-level SLAs
▫ Crude data maps to user requirements such as
 CPU speed maps to Response Time
 Occupied memory size maps to number of concurrent clients
▫ Predictive Strategy for detection of possible SLA violations
▫ Detection interval
 Short measurement intervals may degrade performance
 Long measurement intervals may cause ignorance of heavy SLA violations
Towards autonomic detection of SLA violations in Cloud infrastructures, Future Generation Computer Systems, 2012

16. How migration is done?
• Memory Migration
▫ Pre-copy
 Push phase
 Stop-and-copy phase
 Pull Phase
▫ Pure demand-migration
• File System Migration
▫ In case of distributed file system, there is no need to copy
▫ Alternatively, copy only changed local files to the destination using Virtual
Machine Manager’s API.
S. Venkatesha, S. Sadhu, S. Kintali, and S. Barbara, "Survey of virtual machine migration techniques" - Memory, 2009

17. How migration is done?
• Network Migration
▫ If both source and destination are on same LAN switch
 an unsolicited ARP reply from the migrating host is provided
▫ Alternatively, on a switched network
 the migrating OS can keep its original Ethernet MAC address, relying on the
network switch to detect its move to a new port
• Device Migration
▫ Three type of device support
 Emulation
 Virtualization
 Non-migratable
S. Venkatesha, S. Sadhu, S. Kintali, and S. Barbara, "Survey of virtual machine migration techniques" - Memory, 2009

18. Migration: A Performance Evaluation
• Testbed specification
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6 Servers (1 head node, 5 VM hosts)
Intel Xeon (2.33 GHz Quad-core with 2x6MB L2 Cache)
4GB memory and 7200rpm hard drive
64-bit Ubuntu Linux 8.04 Server Edition
Apache 2.2.8 and MySQL 5.2.4-2
• Workload
▫ Olio as a Web 2.0 application (http://incubator.apache.org/olio/)
▫ Faban Load generator (http://faban.sunsource.net)
• Experiments
▫ 10 minute and 20 minute benchmark runs with 600 concurrent users
Cost of virtual machine live migration in clouds: A performance evaluation, International Conference on Cloud Computing, 2009

19. Migration: A Performance Evaluation
Cost of virtual machine live migration in clouds: A performance evaluation, International Conference on Cloud Computing, 2009

20. Migration across data centers
• Need for VM mobility across data centers
▫
▫
▫
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Data center maintenance without downtime
Disaster avoidance
Data center migration/expansion
Workload balancing across multiple sites
• Issues
▫
▫
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RTT is 1,000 times greater than sub-networks, ‘word wide wait’
Trust to a remote execution environment
Interoperability at the level of Web Services, Java etc
Migration across multiple domains are vulnerable to security exploits

21. Related Work: Migration over MAN/WAN
[FGCS’06]
• Introduced an intermediate traffic controller to facilitate migration
which consists of:
▫ VM Traffic Controller
 Provisioning of network resources and the re-provisioning of the IP tunnel to
ensure seamless layer
▫ AAA (Authentication, Authorization and Accounting)
 Pre-allocation of extra VM-resources required for migration
▫ DRAC (Dynamic Resource Allocation Controller)
 Exposes a service-oriented API for coupling with applications
▫ Preservation of TCP and higher-level sessions
 Dynamically configured IP tunnels allow client connectivity
“Seamless Live Migration of Virtual Machines over the MAN/WAN”, Elsevier Future Generation Computer Systems 2006

22. Related Work: HP Cluster Extension and
Microsoft Hyper-V™
• HP Cluster Extension (CLX) provides flawless mirroring capabilities for
disaster recovery
• VM data is already replicated in single data center cluster
▫ Modifications to spread it across multi-site:
 Multi-site Disaster Recovery solution is implemented
 CLX enables Hyper-V Live Migration across sites
(VMware, Hyper-V, HP-VM and AMD-V)
Our limitation is non-availability of peer referenced or published
material of these architectures to discuss their techniques in detail

23. Proposed Solution
• Security
▫ Layer 2 Link Encryption (IEEE 802.1AE) may be used to help ensure privacy
and confidentially
▫ Token based security - Authorization message sequence to thwart resource
theft
• 1,000 times rise in RTT doesn’t matter much because
▫ All states will be transferred before the switch
▫ Downtime will be based on the time required in redirection
 Which is only 5-10 times than the intra-LAN setup

24. Conclusion

25. Conclusion
• Virtual machine migration provide significant benefits in cloud
computing
• State of the art work is already done on resource monitoring, live VM
migration over the LAN and MAN/WAN
• Downtime is 60ms to 3s which they assume is negligible
• Small transient spikes does not trigger needless migrations, if threshold
or SLAs are exceeded for sustained time
• A slowdown is expected due to cache warm-up at the destination after
migration
• Hybrid approach has been suggested to harness the benefits of all
technqiues