Virtualization - Distributed Operating Systems - Lecture Slides, Slides of Operating Systems

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Virtual Machine and its Role in

Distributed Systems

Virtualization

• Virtualization deals with “extending or replacing

an existing interface so as to mimic the behavior

of another system”

• Virtual system examples: virtual private network

(VPN), virtual memory, virtual machine

• Reduce costs by consolidating services onto

the fewest number of physical machines

http://www.vmware.com/img/serverconsolidation.jpg

Non-virtualized Data Centers

• Too many servers for too little work
• High costs and infrastructure needs
  • Maintenance
  • Networking
  • Floor space
  • Cooling
  • Power
  • Disaster Recovery

VM workload multiplexing

• Multiplex VMs’ workload on the same group of physical servers - Aggregate multiple workload. Estimate total capacity need based on aggregated workload - Performance level of each VM be preserved Separate VM sizing VM multiplexing s 1 s 2 s 3 **_We expect s 3 < s 1

• s

Benefit of multiplexing!_**

So, it is just like Java VM, right?

Thee Virtualization Approaches

Full Virtualization Paravirtualization Hardware-assisted Virtualization

Full Virtualization

• Everything is virtualized
• Full hardware emulation
• Emulation = latency

Pros and Cons – Full

Virtualization

• Pros
  • Disaster recovery, failover
  • Virtual appliance deployment
  • Legacy code on non-legacy hardware
• Cons – LATENCY of core four resources
  • RAM performance reduced 25% to 75%
  • Disk I/O degraded from 5% to 20%
  • Network performance decreased up to 10%
  • CPU privileged instruction dings nearing 1% to 7%

Paravirtualization

• OS or system device drivers are virtualization aware

Requirements:

• OS level – recompiled kernel
• Device level – paravirtualized or “enlightened” device drivers