Virtual Machine Options

As Virtualisation makes it relatively easy to setup a large number of systems, it can help you configure a large number of systems. Each dedicated to a specific service. To that end, it can be separated into 5 different categories.

• Application Level
• Platform-level VMs
• Paravirtualization
• Hardware-assisted Virtualisation
• Bare-metal Virtualisation

Application Level

Systems like WINE are application level virtualisations. They allow the installation of a single application that were designed to be run on an entirely different system.

Platform-level VMs

Applications such as VirtualBox or VMware Player are platform-level VMs. They emulate systems to allow for contained systems to have their own hardware that systems can be installed against.

Paravirtualization

While similar to Platform-level VMs, they work with fewer resources and usually require a specialised kernel such as Xen.

Hardware-assisted Virtualisation

A hardware interface where VMs have access to hardware features of the CPU such as VMX/SVM flags on Intel/AMD chips respectively.

Bare-metal Virtualisation

Some VM systems include a minimal operating system dedicated to VM operation. Two examples of this are Citrix XenServer and VMware ESX.

Notes

The KVM solution that comes with RHEL6 is known as hypervisor, a VM monitor that supports the running of multiple operating systems concurrently on the same CPU. KVM replaces the previous default of Xen.

KVM has replaced Xen in many open-source operating systems. XenSource which is owned by Citrix started working with Microsoft after RHEL5 was released.

Hard Drives and Linux (snippet)

SATA or Serial Advanced Technology Attachment

Systems now with port multipliers, can easily be configured to have 16 drives through SATA. Older systems could only handle 4 through PATA (Parallel Advanced Technology Attachment).

SCSI or Small Computer Systems Interface

Depending on the SCSI hardware, you could have up to 31 hard drive devices connected at a time.

Pick 'n' Mix

While you can combine these in as many configurations as your hardware will allow, the Linux boot files from /boot/ works on only one of the first two hard drives. If Linux is installed on the second drive, you'll need other media recognised by the BIOS/UEFI to get access to it.

The caveat to this however is that Linux doesn't have to be installed to a local drive. There are options that allow it to be placed on SAN (Storage Area Network), DASD (Direct Access Storage Device), hardware RAID devices (Redundant Array of Independent Disk) and more.