Before Virtualisation

• Single O/S Image per machine
• Software and Hardware tightly coupled
• Running multiple applications on the same machine can create conflicts
• Underutilised resources
• Inflexible and costly infrastructure
• Datacenter space taken up in multiple physical servers
• High Management, Support and Operating costs

After Virtualisation

• Hardware independence of operating system and applications
• Virtual machines can be provisioned to any system
• Can manage OS and application as a single unit by encapsulating them into virtual machines
• Power Savings
• Rack space savings
• Feature rich flexibility (vMotion, Storage vMotion, DRS, HA)
• Rapidly provision test and development servers

Virtual Infrastructure now

While virtualization has been a part of the IT landscape for decades, it is only recently (in 1998) that VMware delivered the benefits of virtualization to industry-standard x86-based platforms which now form the majority of desktop, laptop and server shipments. A key benefit of virtualisation is the ability to run multiple O/S’s on a single virtual system and share the underlying hardware resource

There are 2 types of architecture – Hosted architecture (VMware Workstation) and Bare metal Architecture (ESX/ESXi)

We can now take advantage of features such as

• The latest generation of x86-based systems feature processors with 64-bit extensions supporting very large memory capacities. This enhances their ability to host large, memory-intensive applications, as well as allowing many more virtual machines to be hosted by a physical server deployed within a virtual infrastructure.
• The VMKernel runs individual VMMs for each VM responsible for the execution of the VM
• The VMM which is a thin layer providing virtual x86 hardware to the overlying O/S including memory management, CPU scheduling, networking and storage
• Hardware Assist (Intel VD and AMD V)
• Paravirtualisation hardware
• DirectPath
• Direct Memory Access
• AMD RVI and Intel EPT
• Emulated Hardware
• DRS
• HA
• sDRS
• I/O Control for Networking and Storage
• NPIV
• Passthrough devices
• Shares, Reservations and Limits
• Resource Pools
• Clustered file system VMFS
• Raw Disk Mappings
• 3 Virtual Disk types (Eager zeroed thick, Lazy Zeroed thick and Thin)
• Memory reclamation techniques