ESXI details

ESXI : a hypervisor with following feature

Security:
              Memory Hardening: The ESXi kernel,  user-mode applications and executable components are kept in a random and non predictable memory space
              Kernel module integrity:  Digital signing ensures the integrity and authenticity of modules, drivers, and applications as they are loaded by VMkernel
             Trusted Platform Module (TPM): A hardware element that creates a trusted platform and enables  affirmation that the boot process and all drivers loaded are genuine.
              UEFI secure boot: applicable for the systems that support UEFI secure boot firmware whre a digital certificate is chained with VIBs(VMware infrastucture bundle).  a verifier checks that digital certificate before all processes during boot time

VMware virtual network

Storage adapters:
1. Buslogic parallel
2. LSI Logic parallael
3. LSI Logic SAS: has a serial interface
4. VMWare Paravirtual SCSI: greater output and lower CPU usage
5. AHCI SATA controller: Provide access to virtual disks and CD/DVD devices.
6. Virtual NVMe: for attaching and accessing flash storage devices to the pCI express bus.

Network Adapters:
1. Flexible: can function as Vlance or VMXNET adapter
2. E1000-E1000E: High performance adapter available
3. VMXNET3 is available only with VMWare tools
4. SR-IOV pass through: VMs and physical adapters exchange data without involving VMkernel.
                  available in : ESXI 5.5, RHEL 6 windows server 2008  R2
5. vSphere Direct Path I/O : allows VMs to access physical PCI network functions on platforms with an I/O memory management unit.
                  • Hot adding and removing of virtual devices • Suspend and resume
                  • Record and replay • Fault tolerance • High availability
                  • VMware vSphere® Distributed Resource SchedulerTM: Limited availability. The                                 virtual machine can be part of a cluster, but cannot migrate across hosts.
                  • Snapshots.
6. PVDRMA: paravirtualized device that provides improved virtual device . provides RDMA-like interfaces  

provisioning of virtual disks

Thick provisioning:
consume all disk paces irrespective of data consumption
              Thick Provision Lazy-Zeroed: Space required for the virtual disk is allocated during                           creation. Data remaining on the physical device is not erased during creation, but is zeroed                   out on demand at a later time on first write from the virtual machine. This type is the                           default disk type
             Thick Provision Eager-Zeroed: Space required for the virtual disk is allocated during                          creation. Data remaining on the physical device is zeroed out when the disk is created

Thin Provision: A thin-provisioned disk uses only as much datastore space as the disk initially
needs. If the thin disk needs more space later, it can expand to the maximum capacity allocated to it.

Virtual HW on VM

* Upto 128 VCPUs
* Upto 6TB of RAMs
* Upto 10 NICs


VMCI: infrastucture that maintain communication between VMs and host operating system
             Benefits: without VMCI the communication was to be over network layer which would add                 overheads over communication.VMCI can go up to nearly 10 Gbit/s with 128 K sized queue               pairs.

VM file details

 A configuration file (.vmx)
. • One or more virtual disk files. The first virtual disk has files VM_name.vmdk and VM_name-flat.vmdk.
• A file containing the virtual machine’s BIOS settings (.nvram).
• A virtual machine’s current log file (.log) and a set of files used to archive old log entries (-#.log).
• Swap files (.vswp) used to reclaim memory during periods of contention.
 • A snapshot description file (.vmsd). This file is empty if the virtual machine has no snapshots.

In addition to the current log file, vmware.log, up to six archive log files are maintained at one time. For example, -1.log to -6.log might exist at first. The next time an archive log file is created, for example, when the virtual machine is powered off and powered back on, the following actions occur: the -6.log is deleted, the -5.log is renamed to -6.log, and so on. Finally the previous vmware.log is renamed to the -1.log.