VMware vSphere Fundamentals

VMware vSphere is a platform for running and managing virtual machines on physical servers. ESXi supplies the hypervisor on each host, while vCenter Server organizes hosts, clusters, storage, networks, and virtual machines through one management plane.

itVirtualization, containers, and orchestration

Don't Panic — VMware vSphere Fundamentals

VMware vSphere is the arrangement that lets several physical servers behave like a managed home for virtual machines. A VM gets virtual processors, memory, disks, and network adapters. The physical host supplies the actual machinery, which is rather less magical once you notice the cables still exist.

The important split is between ESXi, the bare-metal hypervisor that runs a VM, and vCenter Server, the management layer that organizes hosts, permissions, and cluster policy. ESXi can keep running an existing VM when vCenter is unavailable. vCenter is still where coordinated work happens, so losing it turns administration from orderly to considerably more manual.

A VM is not one object. It is a chain: execution on an ESXi host, files on a datastore, and traffic through a port group, a virtual switch, and physical uplinks. That is why an inventory entry can look perfectly healthy while the guest cannot reach storage or a network. The inventory is a map. It is not the territory, and maps are famously poor at carrying packets.

Clusters add DRS for placement and balancing, and HA for restarting eligible VMs after a host failure. Those names sound like they might form one heroic robot. They do not. HA restarts a guest; it does not preserve continuous execution. DRS can place or move compatible workloads; it does not repair an application. Both rely on spare capacity, accessible VM files, and working networks.

Storage provides another useful correction to optimism. A snapshot redirects writes to delta files so you can roll back a controlled change. It shares the VM's storage chain, so it is not an independent backup. Thin-provisioned disks also grow into real capacity later, when they have developed opinions about the timing.

The rest is disciplined dependency work. Reservations, limits, and shares alter behavior when resources are scarce. Standard and distributed switches still depend on correct physical network settings. Updates proceed from vCenter to ESXi, then Tools and virtual hardware, because compatibility does not enjoy surprises.

Read the Intro for the architecture and failure boundaries. Use Slides for the component map, Cheatsheet for the operational signals, and Reference for the official documentation. That route turns vSphere from a large menu of acronyms into a system you can reason about.

Don't Panic — VMware vSphere Fundamentals

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