Vmware Virtualization Basics

  • Below are the needs for a Data Center Virtualization(DCV):
    • Availability – DCV helps to achieve zero down-time for apps & VMs.
    • Scalability – DCV helps to scale underlying hardware without any impact to applications.
    • Optimization – DCV helps to utilize available hardware resource more effectively.
    • Management – DCV helps to manage VMs more efficiently.
  • Each Virtual Machine (VM) has its own OS, dedicated virtual hardware(CD-Drive, Hard disc, Network card) and real applications running on each VM.
  • Hypervisor – Resource management for VMs.
    • Type-1: Bare-metal: Installing Vmware ESXi (a hypervisor) directly on a server(ESXi Host).
    • Type-2: Hosted: Installed as an application on top of an OS(like Windows, Linux). Ex: Vmware Workstation.
  • Features:
    • Snapshots : Take a snap of a VM along with its all data. Useful for recovery in case of crash after a patch update.
    • Image backup : VM Image backup similar to snapshots.
    • “Hot Add” : Adds more CPU and memory to servers without any downtime.
    • “Thin Provisioning” : VMs are allowed to use disk on demand.
    • “Thick provisioning” : VMs are hard-allocated the configured memory size.
    • “VM storage profiles” : an Automatic way to map servers to a storage class so that storage is used efficiently and effectively.

vCenter

  • To handle/manage many ESXi hosts from a single point.
  • Manage up to 1,000 hosts and 10,000 virtual machines
  • Vcenter server is installed on a host. (can be installed as one of the VMs on an ESXi host- Linux vCenter Server Appliance.ovf)
  • Management features:
    • vMotion – migrate VM from one ESXi host to another.
      • A VM is a chunk of memory on an ESXi host.
      • Doesn’t need shared storage (from ESXi 5.0)
    • DRS – Distributed Resource scheduler – Load balance across ESXi host by vMotion. Automates the vMotion based on server load.
    • DPM – Distributed power Management – to power off unused ESXi host and power-on when needed.
      • Leverages on DRS to power-off ESXi host during less-activity period.
    • Storage vMotion – move VM’s hard disc from one host to another.
    • Storage DRS
      • Automate storage vMotion.
    • Storage I/O control:
      • Control busy VMs from accessing shared datastore so that other critical VMs will get their portion.
    • vSphere Data protection (VDP) – to Backup VMs.
      • Image-based back up (Bare-metal backup)
      • Can restore individual files from that image-based backup.
    • HA (High Availability) – restart VMs on another host when there is hardware problem.
      • Monitors status of ESXi host, VMs, and critical applications running on a VM.
      • HA is configured via vCenter but the HA services do not relay on Vcenter for its operation.
      • If an ESXi host fails , the cluster will direct the surviving ESXi host to restart the failed VMs.
      • If an VM fails, (communication failure between HA software running on VM and ESXi host), that specific VM can be restarted.
      • Minimize down time caused by hardware failures.
    • Fault Tolerance (FT) – uninterrupted availability of VMs
      • Mirror a VM image on another ESXi host. If one host crashes, VM on another ESXi starts.
      • Works fine within a data center.
      • Applications, running on VMs, are not interrupted by hardware failures. Zero downtime.
      • VM files must be stored on shared storage.
    • Vsphere Replication – copy VMs(entire Vsphere ESXi) to another remote site for disaster recovery purpose.
      • Choose a point in time, to recover the VMs at that specific time.

Storage:

  • Shared storage:
    • A storage array, where VM images are stored, that are visible to multiple ESXi hosts.
    • Features that requires shared storage:  DRS, DPM, Storage DRS, HA and FT.
  • Storage Types:
    • vSphere supports FC, FCoE, iSCSI and NFS for shared storage and also supports local hard disc storage.
  • VSA – vSphere Storage Appliance
    • Creates a shared storage from the local storage (local hard disc) in an ESXi host.
  • vFlash:
    • A pool of SSDs in ESXi hosts.
    • To use vFlash, have atleast one SSD drive on an ESXi host and Configure the VMs to use vFlash storage.
    • Improves VMs read performance.
    • ‘vSphere Flash Read cache’
  • Datastore:
    • VMs are stored in containers called “Datastore”
    • Logical storage volume where the VM files and ISO images are stored.
    • Two types: VMFS and NFS. VMs doesn’t even know about underlying storage devices.
    • VMFS:
      • Built on local, FC, Fcoe, iscsi storages.
    • NFS:
      • Built on NAS – Network Attached Storage.

 Networking:

  • Virtual NICs are created for each VM and hence a need for a virtual switch in an ESXi host.
  • Two types of virtual switch – Standard and distributed switch.
    • Standard switch – Pre-built within ESXi host. Provides basic connectivity and management feature at ‘Host’ level.
      • Managed through vcenter or directly from ESXi host.
    • Distributed switch – Qos to prioritize traffic of certain VMs and other features like LLDP.
    • Networking features: VLANs, traffic shaping, port mirroring, QOS/DSCP for traffic prioritization, CDP/LLDP for device discovery.

vSphere Editions:

  • Essential – Basic package with ESXi hypervisor alone.
  • Essential Plus – Hypervisor, vmotion, HA, DP and vsphere replication.
  • Standard –  Essential plus + storage Vmotion and FT.
  • Enterprise  – Standard + DRS, DPM.
  • Enterprise Plus (Advanced with all feature sets) – Enterprise + Storage DRS and Distributed switch.
  • vCenter Operations Manager:
    • A program that, works with vCenter, monitor and manages health, risk and efficiency.
    • Dynamic adjusting threshold.
    • Monitor current capacity.
  • vCenter configuration manager:
    • Configuration change discovery and correlation. Works with vCenter.
    • Used by public-traded company to track configuration changes as they are subject to regulatory bodies.
    • Configuration analysis with third-party standards.
    • Automatically correlating changes to performance issues.
  • vCenter Site Recovery Manager(SRM):
    • Orchestration tool for disaster recovery.
    • Uses vSphere replication to replicate select VMs or entire environment for disaster recovery/fallback.

 Reference:

Free e-learning course in Vmware Education – A recommended course before doing VCA-DCV online Exam.

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