VMware Complete Q&A Guide
50 Essential Questions for vSphere Administration
Version 1.0 | January 2026
📑 Table of Contents
1-10: Infrastructure & Troubleshooting |
11-20: Advanced Features & Management
21-30: Storage & Replication |
31-40: Security & Operations |
41-50: Latest Features & Automation
Module 1: Infrastructure & Troubleshooting (Q1-Q5)
Q1: How do you troubleshoot a disconnected ESXi host in vCenter?
- Check network connectivity and physical cable
2. Verify firewall rules and vCenter access
3. Review logs: /var/log/vmkernel.log
4. Restart management agents: services.sh restart
5. Check SSL certificate validity
6. Verify correct IP address, port, and credentials
Q2: What are the differences between thick and thin provisioning?
THICK: Pre-allocates entire disk space immediately. Two types: Eager Zeroed (all blocks zeroed) and Lazy Zeroed (zeroed on first write). Better performance, but wastes space.
THIN: Allocates space as needed. Saves space, but slower performance. Risk of disk full if not monitored properly.
Q3: Explain the process of patching an ESXi host.
- Check available patches: esxcli software vib list
2. Download patches from VMware website
3. Put host in Maintenance Mode
4. Remediate using Update Manager or vSAN
5. Reboot host if required
6. Exit Maintenance Mode and verify cluster status
Q4: How do you troubleshoot a VM stuck at 95% during power on?
VM is loading drivers. Wait for 10-15 minutes. Check:
1. CPU/Memory contention on host
2. Storage latency: esxtop – disk queue
3. VM’s boot order and firmware settings
4. Check vmkernel logs for errors
5. Verify VMFS datastore health
6. If stuck permanently, try reverting to snapshot
Q5: What is the use of VMware Tools, and what are its components?
COMPONENTS: Memory balloon driver, Quiesce driver, Sync driver, Heartbeat monitor.
USE: Enables better VM performance, host-guest communication, snapshot consistency, time synchronization, and graceful shutdown.
Provides device drivers for faster I/O and enhanced mobility features.
Module 2: Networking & Advanced Features (Q6-Q10)
Q1: Describe the different VMkernel adapters and their roles.
vmk0: Management traffic (vCenter, SSH access)
vmk1: vMotion – VM live migration
vmk2: Storage (iSCSI, NFS)
vmk3: VSAN – vSAN cluster communication
vmk4: FT logging – Fault Tolerance replication
vmk5: Replication – vSphere Replication
Q2: What is the use of vCenter HA and how do you configure it?
Provides high availability for vCenter Server with automatic failover. Configuration: Configure HA manually or through UI. Requires 3 vCenter instances (active+passive nodes). Shared storage and network required. Auto-switchover on failure.
Q3: What are the steps to enable SSH on an ESXi host?
- Connect to DCUI console
2. Press F2 to enter system customization
3. Enter root password
4. Navigate to ‘Troubleshooting Options’
5. Select ‘Enable SSH’
6. Or use vCenter: Select host > Configure > Services > SSH > Start
Q4: How do you upgrade VMware Tools across multiple VMs?
Method 1: vCenter UI – Right-click cluster > Upgrade VM Tools
Method 2: Guest OS native installer
Method 3: PowerCLI: Update-Tools -VM $vm
Ensure VMs support new Tools version, schedule for maintenance window.
Q5: How does Storage DRS work and when is it triggered?
Analyzes VMFS datastore I/O latency and space utilization. Triggers migration when: 1) Space utilization > threshold, 2) Latency > threshold, 3) Load imbalance detected. Requires DRS cluster license and multiple datastores.
Module 3: Licensing & VM Management (Q11-Q15)
Q1: What is the difference between vSphere Standard and Enterprise Plus?
STANDARD: Basic features – vMotion, HA, snapshots. 8vCPU per license.
ENTERPRISE PLUS: Advanced – vSAN, DRS, Storage DRS, Replication, Horizon licensing, Hot Add, TPM 2.0 support. 32vCPU per license. More cost-effective for large deployments.
Q2: How do you handle a PSOD (Purple Screen of Death)?
Indicates kernel panic. Steps:
1. Document error code and logs
2. Reboot host to recovery mode
3. Check /var/log/vmkernel.log
4. Verify hardware (RAM, CPU, firmware)
5. Update ESXi to latest patch
6. Review recent changes (drivers, patches)
Q3: What are the types of VM migration in vSphere?
- vMotion: Live migration with zero downtime
2. Storage vMotion: Migrate VM files between datastores
3. Cross-vCenter vMotion: Migrate across vCenter instances
4. Cold Migration: Power off, then migrate
5. Shared-Nothing Migration: Both CPU and storage migration
Q4: What is the role of the vSphere Web Client?
Replaces C# client for managing vSphere infrastructure. HTML5-based, browser-independent. Features: VM management, cluster management, storage management, networking, security policies, performance monitoring, and reporting.
Q5: How do you backup and restore a vCenter Server Appliance?
Backup: Use vCenter Server Backup UI or vSphere Client. Method: scheduled or on-demand.
Restore: 1) Deploy fresh vCSA, 2) Run Restore wizard, 3) Point to backup location, 4) Recover database and config files, 5) Verify all services running.
Module 4: Affinity & Storage Features (Q16-Q20)
Q1: Explain VM affinity rules with examples.
ANTI-AFFINITY: VMs stay on different hosts (e.g., database + app server)
AFFINITY: VMs stay on same host (latency-sensitive apps)
required: Must follow rule, preferred: should follow if possible
Example: 2 VMs hosting redundant services must not run on same host for availability.
Q2: What is VMkernel and why is it important?
Core OS of ESXi hypervisor. Handles: resource allocation, device drivers, virtual machine communication, I/O operations.
Importance: Bridges VM and physical hardware. Manages memory pages, CPU scheduling, interrupt handling. Foundation for all VMware features.
Q3: How does VMware vMotion ensure data integrity?
- Transfers memory state while VM running
2. Tracks memory dirtied during migration
3. Source host flushes dirty pages at end
4. Registers updated, destination takes over
5. Storage accessible via shared datastore
6. Zero downtime, transparent to guest OS
Q4: What are the requirements for enabling Fault Tolerance?
- vSphere Enterprise Plus license
2. FT logging vmkernel adapter (vmk4)
3. Hosts with same CPU family
4. Sufficient bandwidth (VMware recommends 1 Gbps)
5. VM must have single vCPU (8.0+), max 4vCPU
6. No USB/serial devices, no snapshots
Q5: How do you configure a syslog server in ESXi?
Via DCUI: Troubleshooting > Configure Syslog
Via CLI: esxcli system sysconfig set –loghost=syslog://host:port
Via vCenter: Host > Configure > Advanced System Settings > Syslog
Verify: esxcli system syslog config get
Module 5: RDM & Replication (Q21-Q25)
Q1: Explain the usage of RDM and when to use it.
RAW DEVICE MAPPING: Direct access to physical disks/LUNs. Types: Physical (RDM), Virtual (pRDM)
USE CASES: Databases requiring direct disk access, clustering (MSCS), SAN snapshots, specific driver requirements
ADVANTAGES: Direct SAN access, better performance
DISADVANTAGES: No snapshots, lower portability, complex management
Q2: What are the differences between vSphere Replication and SRM?
REPLICATION: Continuously replicates VM data to target site. RPO minutes. Agent-based or array-based.
SRM: Site Recovery Manager – orchestrates failover/failback. Manages recovery plans, network re-configuration. Higher licensing cost but complete DR solution.
REPLICATION is component; SRM is comprehensive DR orchestration.
Q3: How do you analyse and read the vmkernel log?
Location: /var/log/vmkernel.log
Key fields: timestamp, event type, VM/process name, error code
Common issues: storage failures (SCSI), memory errors, driver issues
Tools: grep for errors, tail -f for real-time, vsyslog for web access
Example: grep ‘error’ vmkernel.log | grep device
Q4: What are the high availability admission control policies?
- PERCENTAGE: Reserve 25/50% cluster capacity
2. SLOT: Based on largest VM (CPU+Memory)
3. FAILOVER HOSTS: Specify failover capacity per host
4. DISABLED: No admission control (risky)
Q5: How do you secure an ESXi host?
- Enable BIOS/UEFI security features (TPM, Secure Boot)
2. Change default SSH/IPMI passwords
3. Disable unnecessary services
4. Configure firewall rules
5. Enable lockdown mode
6. Use vSphere Trust Authority for encrypted VMs
7. Regular patch management
Module 6: Content Libraries & Snapshots (Q26-Q30)
Q1: What is the use of content libraries in vSphere?
Repository for VM templates, vApps, and ISO files. Types: Local (one vCenter) and Subscribed (clone remote library).
BENEFITS: Version control, role-based access, rapid deployment, consistency across organization.
CAN SYNC with vSAN, OVA files, and other libraries.
Q2: Describe the lifecycle of a VM snapshot.
- CREATE: Snapshot captures VM state (memory, CPU, disk)
2. BACKUP: Changes go to delta disk
3. MULTIPLE: Create chain for point-in-time recovery
4. CONSOLIDATE: Merge delta disks back to parent
5. DELETE: Remove snapshot, commit changes
WARNING: Long chains degrade performance, consolidate regularly.
Q3: What are the supported vCenter deployment models?
- vCenter Server Appliance (vCSA) – recommended
2. vCenter Server on Windows – legacy
3. Multi-site deployment – >1000 hosts per vCenter
4. vCenter HA – 3-node cluster for HA
5. Embedded PSC – single vCSA with embedded Platform Services Controller
Q4: How do you monitor and resolve high CPU usage in a VM?
MONITOR: vCenter Performance tab, RVTools, esxtop
CHECKS: 1) Guest OS CPU usage 2) VMware balloon inflation 3) CPU ready time 4) Host CPU contention
RESOLVE: Increase vCPU allocation (if available), optimize guest apps, migrate VM to less loaded host.
Q5: Explain the boot process of an ESXi host.
- BIOS/UEFI power-on self test (POST)
2. Boot loader loads kernel (vmkernel)
3. VMkernel mounts root FS
4. Loads drivers and modules
5. Starts vmks services (hostd, vpxa)
6. Register VMs from datastore
7. vCenter connection attempt
8. Ready for operations
Module 7: vSAN & Templates (Q31-Q35)
Q1: What are the key components of vSAN?
- CAPACITY TIER: Flash or HDD storage
2. CACHE TIER: SSD for write buffer
3. METADATA: Object metadata tracking
4. DOM: Distributed Object Manager
5. CLOMD: Cluster monitoring daemon
6. VSAN file system: Distributed storage fabric
REQUIRES: 3+ nodes, compatible hardware, vSAN license.
Q2: How do you convert a VM to a template and deploy from it?
CONVERT: Right-click VM > Clone > Clone to Template
DEPLOY: Right-click Template > New VM from Template, customize settings
ALTERNATIVE: Export VM as OVA, import as template
UPDATE: Convert template back to VM, modify, reconvert
BENEFIT: Faster deployment, consistency, version control.
Q3: What are the differences between NFS and VMFS datastores?
NFS: Network File System, shared access, no VMFS volume format needed, easy to provision, no SAN required
VMFS: Virtual Machine File System, block-level access, optimized for VMs, supports raw device mapping, better for SAN environments
NFS simpler setup; VMFS better performance for VM workloads.
Q4: How do you perform a vCenter upgrade?
Backup current vCenter first!
1. Download target version ISO
2. Stop all services
3. Run upgrade installer
4. Provide database credentials
5. Accept EULA and specify upgrade options
6. Monitor installation progress
7. Verify all services, test connectivity
8. Update SSL certificates if needed
Q5: What are the different types of logs available in vSphere?
VMKERNEL: /var/log/vmkernel.log – kernel events
VPXA: /var/log/vpxa.log – vCenter agent
HOSTD: /var/log/hostd.log – host daemon
AUDIT: /var/log/audit.log – security events
SYSLOG: Centralized logging
VMSWD: /var/log/vmswd.log – watchdog
Module 8: Distributed Switch & Trust Authority (Q36-Q40)
Q1: How does Distributed Switch backup and restore work?
BACKUP: Export switch config as backup file via vCenter
RESTORE: Import backup to restore VLAN, port group, and traffic shaping settings
INCLUDES: Port group config, VLAN settings, load balancing, security policies
USE CASE: Disaster recovery, migrating DVS between vCenters.
Q2: Explain vSphere Trust Authority and its use case.
Enables encrypted VMs at rest and in transit. Components: Key Provider, vSAN Encryption, VM Encryption
USE CASES: Healthcare (HIPAA), Finance (PCI-DSS), Government compliance
BENEFIT: Transparent encryption, no performance penalty, keys stored separately
REQUIRES: vSphere Enterprise Plus, compatible Key Provider.
Q3: What is Proactive HA in vSphere?
Predicts hardware failures using Skyline logs. Automatically migrates VMs from soon-to-fail hosts to healthy hosts.
REQUIRES: vSAN or supported storage arrays
BENEFIT: Prevents unplanned downtime before hardware fails
RELIES ON: ML predictions from VMware Skyline analytics.
Q4: What are the requirements for Cross vCenter vMotion?
- vSphere Enterprise Plus licenses
2. Network connectivity between vCenters
3. Enhanced Linked Mode (optional, recommended)
4. VMs on VMFS3/VMFS5/VMFS6 datastores
5. No vSAN datastores (vSAN 6.7+)
6. Compatible VM hardware versions
7. Source and target compatibility check needed.
Q5: How do you manage licenses in vCenter?
- Administration > Licensing > Licenses
2. Add license key via UI
3. Assign licenses to hosts/clusters
4. Monitor license usage and expiration
5. Use License Manager for reporting
6. Set up renewal reminders
7. Verify compliance with ‘License Status’ view.
Module 9: HA & Isolation Detection (Q41-Q45)
Q1: How does host isolation detection work in vSphere HA?
HA agent heartbeats via network/datastore.
ISOLATION DETECTION:
1. Network isolation – can’t reach vCenter/other hosts
2. Datastore isolation – can’t access heartbeat datastore
3. If isolated >15sec: triggers response (restart VMs on other hosts)
RESPONSES: Restart VMs, do nothing, or power off VMs.
Q2: What is the use of tagging in vSphere inventory?
Organize and classify objects (VMs, hosts, datastores).
TAG CATEGORIES: Custom metadata for policies
USE CASES: Cost allocation, compliance tracking, automation rules
EXAMPLES: Environment (prod/dev), Owner, Department
BENEFIT: Enables resource governance and compliance automation.
Q3: How does VMware Skyline assist support teams?
Cloud-based analytics platform.
BENEFITS: Proactive issue detection, capacity planning, health assessment
DATA: Anonymized telemetry from vSpheres
RECOMMENDATIONS: Hardware issues, performance optimization, security advisories
FREE: Included with vSphere, opt-in for features.
Q4: What is DRS score and how is it calculated?
DRS SCORE: 1-5 rating of cluster load balance (1=imbalanced, 5=balanced)
CALCULATION: Based on VM CPU and memory imbalance
FACTORS: CPU utilization, Memory utilization, VM count per host
TRIGGERS MIGRATION: If score falls below threshold for migration level.
Q5: How to troubleshoot VM NIC connectivity issues?
- Check vNIC settings in VM properties
Verify port group exists
3. Check VLAN configuration
4. Verify MAC address not in conflict
5. Review host dvs/vswitch config
6. Ping gateway from guest OS
7. Check firewall rules
8. Review vmkernel.log for NIC errors.
Module 10: Hardware Compatibility & Latest Features (Q46-Q50)
Q1: What is the significance of VM hardware compatibility?
VERSIONS: Hardware version determines CPU/memory/feature support
IMPACT: Newer versions unlock vSphere features, better performance
MAJOR UPGRADES: VM Compatibility: VMX version defines features available
UPGRADE NEEDED FOR: New CPUs, larger memory, new devices, encryption
BACKWARD COMPAT: Older VMs run on newer hosts, but miss new features.
Q2: How do you enable TPM 2.0 support for ESXi?
BIOS: Enable TPM 2.0 in firmware
FIRMWARE: Ensure motherboard supports TPM 2.0
ESXi CONFIG: Hardware version 17+ required
VMs: Enable per-VM via ‘Enable Secure Boot and Firmware Configuration’
BENEFIT: Windows 11 support, Secure Boot, encrypted VMs
REQUIRES: vSphere Enterprise Plus.
Q3: What is Secure Boot in VMware ESXi?
Verifies firmware and boot components digitally signed.
IMPACT: Prevents unauthorized code during boot
VMs: Can enable Secure Boot for Windows 11/Server 2022
IMPLEMENTATION: UEFI firmware required
BENEFIT: Security hardening against rootkits and bootkits
TRADE-OFF: Slight boot performance impact.
Q4: How to automate VM creation using PowerCLI?
PowerCLI Script:
Connect-VIServer $vCenter
$vmhost = Get-VMHost $hostname
New-VM -Name $vmname -ResourcePool $cluster -VMHost $vmhost -MemoryMB 4096 -NumCpu 2 -DiskMB 50000
EXTEND: Add networking, customize, connect to libraries
AUTOMATION: vRealize Automation for templates and lifecycle.
Q5: What’s new in vSphere 8.0 Update 2?
FEATURES: Enhanced Secured-Core compliance, improved vSAN, Compute/Storage optimization
PERFORMANCE: Better CPU efficiency, memory deduplication
SECURITY: Additional cryptography algorithms, enhanced Trust Authority
AUTOMATION: Better integration with Kubernetes
AVAILABILITY: Improved HA/DR capabilities
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VMware vSphere Complete Guide | For IT Professionals & Exam Candidates
This document is for educational and reference purposes.
