Points for VMkernel.
=>Commnication with Service Console
=>Managing resource managment
=>Capability and Flexibility of Vmkernel
=>How it is derived.
=>Is append to vmkernel is possible?
=>Is there any tool to monitor vmkernel ?
VMware ESX Server uses a Linux kernel that loads additional code: often referred to by VMware, Inc. as the "vmkernel". The VMware FAQ states 'ESX Server also incorporates a service console based on a Linux 2.4 kernel that is used to boot the ESX Server virtualization layer'. The Linux kernel runs before any other software on an ESX host, witness the console of a booting ESX machine. No VMkernel processes run on the system during the boot process. After the Linux kernel has loaded, the S90vmware script loads the vmkernel. VMware states that vmkernel does not derive from Linux. The Linux kernel continues running but under vmkernel, providing functions including the proc file system used by the ESX and an environment to run support applications.
In traditional systems, a given operating system runs a single kernel. The VMware FAQ mentions that ESX has both a Linux 2.4 kernel and vmkernel hence confusion over whether ESX has a Linux base. An ESX system starts a Linux kernel first, but it loads vmkernel (also described by VMware as a kernel), which wraps around the linux kernel, and according to VMware does not derive from Linux.
The ESX userspace environment, known as the "Service Console" (or as "COS" or as "vmnix"), derives from a modified version of Red Hat Linux, (Red Hat 7.2 for ESX 2.x and Red Hat Enterprise Linux for ESX 3.x). In general, this Service Console provides management interfaces (CLI, webpage MUI, Remote Console). This VMware ESX hypervisor virtualization approach provides lower overhead and better control and granularity for allocating resources (CPU-time, disk-bandwidth, network-bandwidth, memory-utilization) to virtual machines. It also increases security, thus positioning VMware ESX as an enterprise-grade product.
As a further detail which differentiates the ESX from other VMware virtualization products: ESX supports the VMware proprietary cluster file system VMFS. VMFS enables multiple hosts to access the same SAN LUNs simultaneously, while file-level locking provides simple protection to file-system integrity.
Thanks
Nitin
