Cloud Virtualization considerations:

Snapshots & Migrations

• Snapshot: freeze a copy of virtual machine
  • Identify all pages in disk files, VM memory
  • Use copy-on-write for any subsequent modifications
  • To revert, throw away the copy-on-write pages
• Migration: move a VM to another host
  • Take snapshot (fast)
  • Copy all pages of snapshot (not so fast)
  • Copy modified pages (fast)
  • Freeze virtual machine and copy VM memory
    • Very fast, fractions of a second

Cloning

• Simple clone:
  • Freeze virtual machine
  • Copy all files implementing it
  • Use copy-on-write to speed up
• Linked clone:
  • Take snapshots
  • Original and each clone is a copy-on-write version of snapshot
• VMware Workstation
  • Separates Host OS from virtualization layer
  • Host OS may be Windows, Linux, etc.
  • Wide variety of Guest operating systems