VMware

Monitoring Disk Command Aborts on ESXi: Identifying Storage Overload | Lazy Admin Blog

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When your storage subsystem is severely overloaded, it cannot process commands within the acceptable timeframe defined by the Guest Operating System. The result? Disk Command Aborts. For Windows VMs, this usually triggers after 60 seconds of silence from the storage array.

Aborted commands are a critical red flag indicating that your storage hardware is overwhelmed and unable to meet the host’s performance expectations. Monitoring this parameter is essential for proactive datacenter management.

Here is how you can track these aborts using two primary methods: the vSphere Client and esxtop.

💻 Method 1: vSphere Client (Graphical Interface)

This method provides a visual, historical look at command aborts across your infrastructure.

  1. Navigate to Hosts and Clusters.
  2. Select the object you want to monitor (Host or Cluster).
  3. Click on the Monitor tab, then Performance, and select Advanced.
  4. Click Chart Options.
  5. Switch the metric grouping to Disk.
  6. Select Commands aborted from the list of measurements.
  7. Click OK.

🛠️ Method 2: esxtop (Command Line Interface)

For real-time, granular troubleshooting, esxtop is the definitive tool. It monitors the ABRTS/s (Aborts per Second) field, specifically tracking SCSI aborts.

Steps to Configure esxtop for Aborts:

  1. Open Putty and log in to your ESXi host via SSH.
  2. Type esxtop and press Enter.
  3. Type u to switch to the Disk Device view.
  4. Type f to change the field settings.
  5. Type L to select Error stats.
  6. Press Enter, then press W to save these settings for future sessions.

You will now see the ABRTS/s column. This number represents the SCSI commands aborted by the guest VM during the 1-second collection interval.

📈 Thresholds and Interpretation

If you are deploying a monitoring tool, the critical threshold for ABRTS/s is 1. A value of 1 or higher means SCSI commands are actively being aborted by the guest OS because the storage is not responding.

What is Ideal?

In an ideal scenario, ABRTS/s should always be 0.

What is Real-World?

In a busy production environment, you may see this value fluctuate between 0 and 0.xx. This occurs during “peak hours”—for instance, when multiple servers on the host are running disk-intensive backup operations simultaneously, leading to temporary storage saturation. However, any consistent spike above 1 requires immediate investigation into path failures, array congestion, or complete storage unresponsiveness.

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Fix vCenter Performance Overview Error: “Navigation to the webpage was cancelled” (1014454)

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If your Performance Overview tab is showing a blank screen or a “navigation cancelled” error, it usually means the vSphere Client can’t reach the underlying stats reporting service. This often happens after a DNS change, an upgrade, or when a third-party app steals a required port.

Follow these troubleshooting steps in order to restore your performance charts.

Step 1: Check the vCenter Web Management Service

The performance tab isn’t part of the core vCenter service; it runs on a separate web management service.

  • Log into the vCenter Server.
  • Open Services.msc.
  • Verify that VMware VirtualCenter Management Webservices is started. If it is, try restarting it.

Step 2: Bypass DNS (The .xml Edit)

If vCenter is having trouble resolving its own FQDN, the Performance tab will fail to load.

  1. Navigate to: C:\Program Files\VMware\Infrastructure\VirtualCenter Server\extensions\com.vmware.vim.stats.report\
  2. Open extension.xml in a text editor (as Administrator).
  3. Locate the line: <url>https://vcenter-hostname:8443/statsreport/vicr.do</url>
  4. Change the hostname to the Static IP address of your vCenter server.
  5. Restart the vCenter Web Management Service.

Step 3: Check for Port Conflicts (Port 8443)

Performance Overview uses port 8443. Sometimes other web services (like IIS or Apache) grab this port first.

  • The Test: Stop the “VMware VirtualCenter Management Webservices.”
  • Open Command Prompt and run: telnet <vCenter-IP> 8443
  • The Result: If the port responds while the VMware service is stopped, another application is interfering. You will need to identify that app or change the vCenter web port.

Step 4: Browser & Proxy Settings

The vSphere client uses the local Internet Explorer engine to render the performance tab.

  1. Open Internet Options on your workstation.
  2. Go to the Connections tab > LAN Settings.
  3. Uncheck Use automatic configuration script and Proxy server.
  4. If the issue is only happening on external workstations, ensure the Windows Firewall on the vCenter server is allowing traffic on port 8443.

#VMware #vSphere #vCenter #SysAdmin #Virtualization #Troubleshooting #DataCenter #TechTips #LazyAdmin #CloudAdmin #ITPro

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Top VMware ESXi & vSphere Interview Questions

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Preparing for a Virtualization role? This guide covers everything from legacy ESX vs. ESXi differences to advanced HA and DRS logic.

🔄 The Evolution: ESX vs. ESXi

  • Service Console: ESX had a Service Console (based on RHEL); ESXi is “thin” and has no console, leading to a smaller footprint and faster boots.
  • Hardware: ESXi can be purchased as an embedded hypervisor directly on hardware.
  • Health Checks: ESXi features built-in server health status monitoring.

🛡️ High Availability (HA) 5.0 Deep Dive

In vSphere 5.0, the HA architecture moved from a Primary/Secondary model to a Master/Slave concept using the FDM (Fault Domain Manager) agent.

RoleResponsibilities
MasterMonitors host/VM availability, manages restarts, communicates with vCenter.
SlaveMonitors local VMs, sends status to Master, participates in elections if Master fails.

Heartbeat Mechanisms:

  1. Network Heartbeat: Sent between Master and Slaves every second.
  2. Datastore Heartbeat: Used if the network heartbeat is lost to determine if a host is isolated or has actually failed.

🚀 vMotion & DRS (Distributed Resource Scheduler)

vMotion Prerequisites:

  • Shared storage (required prior to 5.1).
  • GigaBit Ethernet dedicated vMotion network (VMkernel port).
  • Processor compatibility (EVC – Enhanced vMotion Compatibility).
  • No active CD-ROM/ISO mounts or CPU affinity.

DRS Automation Levels:

  • Manual: vCenter suggests migrations; admin executes.
  • Partially Automated: vCenter handles initial VM placement; suggestions for migrations.
  • Fully Automated: vCenter moves VMs automatically based on load.

💾 Storage & Networking Quick Hits

  • vSAN: Aggregates local storage from ESXi hosts into a single shared datastore.
  • iSCSI Port Binding: Used when multiple VMkernel ports are in the same subnet to allow multiple paths to an array.
  • Path Selection Policies (PSP): Fixed, MRU (Most Recently Used), and Round Robin.
  • Key Command Line Tools:
    • esxtop: Live performance data.
    • vmkfstools: Virtual disk management.
    • vmware-cmd: VM management and info.

📊 Hardware Version Comparison

FeatureHW Version 4 (ESX 3.x)HW Version 7 (vSphere 4.x)HW Version 8 (vSphere 5.0)
Max vRAM64 GB256 GB1 TB
Max vCPU4832
USB SupportNoYesYes (incl. 3.0)
NICs per VM41010

🚀 Key Differences in Modern vSphere (7.0 & 8.0)

1. The Architecture Shift: Project Monterey & DPUs

Modern vSphere now supports DPUs (Data Processing Units). Instead of the CPU handling networking and security, these tasks are offloaded to the SmartNIC.

2. Tanzu (Kubernetes Integration)

The biggest change in vSphere 7/8 is that Kubernetes is built directly into the hypervisor. You no longer just manage VMs; you manage “Namespaces” and containers natively on ESXi.

3. vMotion Enhancements (vSphere 7+)

In version 5.0, vMotion would “stun” a VM briefly. Modern vMotion uses a “Claim” mechanism that makes migrating massive VMs (Monster VMs) almost instantaneous with zero performance impact.

4. Scalability Comparison (vSphere 5.0 vs. 8.0)

FeaturevSphere 5.0 (Legacy)vSphere 8.0 (Modern)
vCPUs per VM32768
RAM per VM1 TB24 TB
Hosts per Cluster3296
VMs per Cluster3,00010,000

🆕 2026 Interview Questions: Modern Edition

Q: What is the “vSphere Distributed Services Engine”?

A: It is the feature that allows vSphere to use DPUs (SmartNICs) to offload infrastructure services like NSX and vSAN, freeing up the host’s CPU for application workloads.

Q: What is a “Lifecycle Manager” (vLCM)?

A: In vSphere 7+, vLCM replaced the old Update Manager (VUM). It uses a declarative model (Desired State) where you define an image for a cluster, and the hosts automatically maintain that version/driver level.

Q: What is “vSAN Express Storage Architecture” (ESA)?

A: Introduced in vSphere 8, ESA is a new way of processing data optimized for high-performance NVMe drives, removing the old “Disk Group” (Cache/Capacity) requirement.

Q: How does vSphere 8 handle AI/ML workloads?

A: Through vGPU and Device Groups, allowing VMs to span multiple physical GPUs and utilizing High-Bandwidth Memory (HBM) for massive AI model training.

#VMware #vSphere #ESXi #Virtualization #SysAdmin #TechInterview #vMotion #CloudComputing #LazyAdmin #DataCenter

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How to Change the Default Snapshot Location in VMware ESXi 5

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By default, VMware ESXi stores virtual machine snapshots in the same directory as the parent VM. If your primary datastore is running low on space, taking a new snapshot can fail or, worse, cause the VM to hang.

snapshot

Fortunately, you can redirect these snapshots (and swap files) to a different datastore with more “breathing room.”

Phase 1: vSphere Client Configuration

Before modifying files, we need to tell the VM not to store redo logs with the parent.

  1. Power OFF the Virtual Machine (This is mandatory for the changes to take effect).
  2. Right-click the VM and select Edit Settings.
  3. Go to the Options tab > General > Configuration Parameters.
  4. Click Add Row and enter:
    • Name: snapshot.redoNotWithParent
    • Value: true
  5. Click OK to save and exit.

Phase 2: CLI Configuration (.vmx Modification)

Now we define exactly where those snapshots should go.

  1. Log into the ESXi host via SSH or the local console.
  2. Navigate to your VM’s home directory:Bashcd /vmfs/volumes/[DatastoreName]/[VMName]
  3. Open the .vmx configuration file using the vi editor:Bashvi VMName.vmx
  4. Add the following line to the file, specifying your secondary datastore path:PlaintextworkingDir = "/vmfs/volumes/Secondary-Datastore/snapshots" (Press i to insert text, then Esc followed by :wq to save and exit.)

Phase 3: Reloading the VM

Changes to the .vmx file aren’t picked up until the VM is reloaded in the inventory.

  1. Find your VM’s ID:Bashvim-cmd vmsvc/getallvms | grep [VMName]
  2. Note the ID number (e.g., 13) and run the reload command:Bashvim-cmd vmsvc/reload 13

💡 Pro Tip: Keeping Swap Files in the Original Directory

By default, the workingDir parameter also moves the VM’s .vswp (Swap) file. If you only want to move the snapshots and keep the swap file with the parent VM for performance reasons, add this extra parameter in the Configuration Parameters (Phase 1):

Name: sched.swap.dir

Value: "/vmfs/volumes/Original-Datastore/VM-Directory"

#VMware #ESXi #StorageAdmin #SysAdmin #Virtualization #vSphere #TechTutorial #LazyAdmin #DataCenter #CloudComputing

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How to change the thick or thin provisioning of a virtual disk

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🟢 Converting Thin to Thick (Inflation)

If your datastore has plenty of space and you need to eliminate the performance “write penalty” of a thin disk, you can Inflate it.

  1. Preparation: Power off the VM. Ensure there are no snapshots attached to the VM, as inflation only works on the base .vmdk.
  2. Locate the File: Go to the VM’s Summary tab. Under Resources, right-click the datastore and select Browse Datastore.
  3. The “Inflate” Action: Open the VM folder and find the .vmdk file. Right-click it and select Inflate.
    • Note: If “Inflate” is greyed out, the VM is likely still powered on or is already thick-provisioned.
  4. Finalize: Once the task finishes, you may need to Reload the .vmx file to ensure the vSphere UI reflects the new “Thick” status.

🔵 Converting Thick to Thin (Migration)

Converting back to Thin provisioning is slightly more complex because you cannot “deflate” a disk in place. You must move the data to a new location to reclaim the space.

Method A: Migration (Requires two Datastores)

This is the cleanest way to convert a disk using Storage vMotion or an offline migration.

  1. Power Off the VM (required for standard Migration; not required for Storage vMotion if licensed).
  2. Migrate: Right-click the VM and select Migrate > Change Datastore.
  3. Select Format: In the migration wizard, look for the Select Virtual Disk Format dropdown and choose Thin Provision.
  4. Target: Select a different datastore than the current one. vSphere will copy the blocks, only writing the actual data to the destination, effectively “thinning” the disk.

Method B: Cloning (Single Datastore)

If you only have one datastore, you cannot migrate the VM to itself to change the format.

  1. Right-click the VM and select Clone.
  2. During the clone wizard, select your current datastore as the destination.
  3. In the Disk Format section, select Thin Provision.
  4. Once complete, delete the old “Thick” VM and keep the new “Thin” one.

⚠️ Important Considerations

  • Backups: Always have a fresh backup. Moving or inflating disks is a heavy I/O operation.
  • Lazy vs. Eager Zeroed: When inflating to Thick, vSphere usually defaults to “Lazy Zeroed” (space is reserved, but blocks aren’t cleared until written to). For maximum performance (e.g., for Database logs or VSAN), “Eager Zeroed” is preferred.
  • Space Check: Before converting from Thin to Thick, ensure your datastore can handle the immediate consumption of the entire disk size.

#VMware #vSphere #Storage #ThinProvisioning #ThickProvisioning #SysAdmin #ITPro #Virtualization #LazyAdmin #CloudStorage #TechTips

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How to Fix: Keyboard or Mouse Not Working in a VMware Virtual Machine

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It’s a frustrating classic: you click into your VM, and… nothing. The cursor doesn’t move, or the keyboard acts like it’s unplugged. Usually, this is a “focus” or driver issue rather than a hardware failure.

Here is the “Lazy Admin” checklist to get your inputs back online.

1. The “Focus” Check (The Most Common Culprit)

Virtualization software intercepts your hardware inputs. If the VM window doesn’t have “Focus,” your typing is still going to your host OS.

  • Action: Click anywhere inside the VM console window.
  • Pro Tip: Look at the bottom status bar of your VMware window. If the mouse icon isn’t lit up, the VM isn’t “grabbing” the input.

2. The Wireless Device “Passthrough” Trap

If you are using a wireless USB mouse/keyboard, the VM might have accidentally “claimed” the USB receiver for itself, cutting it off from the host.

  • Action: Go to VM > Removable Devices and ensure your HID (Human Interface Device) is Disconnected from the VM so the host can manage it and pass the input through the software layer instead.
  • Alternative: Remove the USB Controller from the VM settings and re-add it to reset the bus.

3. Driver Conflicts & Optimization

Sometimes, fancy “Gaming” drivers (Logitech G-Hub, Razer Synapse) inside the guest OS conflict with the VMware virtual driver.

  • Action: Uninstall any non-standard mouse/keyboard software inside the VM.
  • Optimization: In VMware Workstation settings, go to Preferences > Input and set “Optimize mouse for games” to Always or Automatic.

4. The Nuclear Option: Reinstall VMware Tools

The VMware Tools package includes the specialized vmmouse driver that handles smooth cursor movement and keyboard mapping. If this is corrupted, your input will fail.

  • Action: 1. Press Ctrl + Alt to release your mouse to the host. 2. Go to VM > Install (or Reinstall) VMware Tools. 3. Use the keyboard (Tab and Spacebar) if the mouse isn’t working to navigate the installer.

5. Troubleshooting the Host (OS-Specific)

If the issue persists, the problem might be a service on your physical computer blocking the input stream.

  • Windows Hosts: Run msconfig to perform a “Clean Boot,” disabling non-Microsoft services to see if a background app is interfering.
  • Linux Hosts: Drop to Run Level 2 to disable start daemons and test the raw input.

#VMware #Virtualization #SysAdmin #ITSupport #TechTips #LazyAdmin #VMwareWorkstation #vSphere #WindowsTips #LinuxTips

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Syslog Server storage logs size calculation

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Upgrading your syslog retention is a great move for troubleshooting depth, but as your math shows, it comes with a significant increase in storage demands. Moving from 4GB to 40GB is a 10x jump, so ensuring your volume can handle the growth is critical.

Here is the breakdown of the calculation and the step-by-step guide to applying these changes.

📊 Syslog Storage Planning

Before modifying configuration files, verify your available disk space. Using your specific requirements for 100 hosts:

VariableCurrent SettingDesired Setting
Max Log Size2 MB10 MB
Rotation Count20 Files40 Files
Retention per Host40 MB400 MB
Total Storage (100 Hosts)4,000 MB (4GB)40,000 MB (40GB)

⚠️ A Note on Scalability

While you are planning for 100 hosts, keep in mind that the VMware Syslog Collector for Windows is officially supported for up to 30 hosts.

  • The Risk: Beyond 30 hosts, the service may stop responding or drop logs without an error message.
  • The Fix: If you need to support 100 hosts reliably, consider deploying multiple collectors or moving to a high-scale solution like VMware vRealize Log Insight.

🛠️ How to Modify Syslog Collector Configuration

To apply your new 10MB / 40 Rotate policy, you must manually edit the configuration XML.

1. Locate and Backup

Before editing, create a copy of the configuration file.

  • vCenter 6.0: %PROGRAMDATA%\VMware\vCenterServer\cfg\vmsyslogcollector\config.xml
  • vCenter 5.5 & older: %PROGRAMDATA%\VMware\VMware Syslog Collector\vmconfig-syslog.xml

2. Edit the XML

Open the copy in a text editor (like Notepad++) and locate the <defaultValues> section. Update the values as follows:

XML
<defaultValues>
    <port>514</port>
    <protocol>TCP,UDP</protocol>
    <maxSize>10</maxSize>
    <rotate>40</rotate>
    <sslPort>1514</sslPort>
</defaultValues>

3. Swap and Restart

  1. Stop the Service: Open services.msc and stop the VMware Syslog Collector.
  2. Replace File: Delete the original config.xml and rename your modified copy to the original filename.
  3. Start the Service: Restart the VMware Syslog Collector.

Lazy Admin Tip: If the logs don’t start flowing immediately, you may need to restart the syslog service on the ESXi hosts themselves to re-establish the connection to the server.

#VMware #vSphere #Syslog #DataCenter #Storage #SysAdmin #ITPro #Virtualization #LogManagement #LazyAdmin #TechGuide

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How to Restart Management Agents on an ESXi Host?

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When an ESXi host appears as “Not Responding” in vCenter, or the Web Client becomes sluggish, you don’t always need to reboot the entire server. Often, simply restarting the Management Agents (hostd and vpxa) will restore connectivity without interrupting your running Virtual Machines.

Method 1: Using the Direct Console User Interface (DCUI)

If you have physical access to the server or a remote management console (like iDRAC, ILO, or IPMI), this is the safest method.

  1. Connect to your ESXi host console and press F2 to customize the system.
  2. Log in as root.
  3. Navigate to Troubleshooting Options using the arrow keys.
  4. Select Restart Management Agents.
  5. Press Enter, then press F11 to confirm the restart.
  6. Once finished, press Esc to log out.

Method 2: Using SSH or Local Shell

If SSH is enabled, you can restart the specific agents individually. This is the preferred “Lazy Admin” method as it provides granular control.

For ESXi 5.x, 6.x, and 7.x/8.x: Run these two commands to restart the host agent and the vCenter agent:

Bash

/etc/init.d/hostd restart
/etc/init.d/vpxa restart

For legacy ESXi 4.x:

Bash

/etc/init.d/hostd restart
service vmware-vpxa restart

Method 3: The “Nuclear” Option (services.sh)

If the individual agent restarts don’t work, you can restart all management services on the host.

Command:

Bash

services.sh restart

⚠️ CRITICAL CAUTION

If LACP is enabled on your Distributed Virtual Switch (DVS), do not use services.sh restart. Doing so can disrupt network connectivity. Instead, restart independent services or schedule a maintenance window.

Method 4: Resetting the Management Network

Sometimes the issue isn’t the agent, but the VMkernel interface itself. You can bounce the management interface (usually vmk0) with this one-liner:

Bash

esxcli network ip interface set -e false -i vmk0; esxcli network ip interface set -e true -i vmk0

The semicolon ensures the interface comes back up immediately after being disabled.

#VMware #ESXi #vSphere #SysAdmin #ITPro #Virtualization #Troubleshooting #LazyAdmin #DataCenter #TechTips #CloudAdmin

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How to get Serial number and System information of ESXi host remotely using putty

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🛠️ Method 1: Using esxcfg-info

The esxcfg-info command is a comprehensive tool that dumps a massive amount of data regarding the host’s configuration. Filtering this with grep is the quickest way to find your serial number.

Command:

Bash

esxcfg-info | grep "Serial Number"
  • What it does: Searches the entire configuration dump for the specific “Serial Number” string.
  • LazyAdmin Tip: If you get too many results, try esxcfg-info -w | grep "Serial Number" to focus specifically on hardware information.

🛠️ Method 2: Using dmidecode (DMI Table Decoder)

If you need more than just the serial number—such as the Manufacturer, Product Name (Model), and UUID—dmidecode is the standard tool. It retrieves data directly from the system’s Desktop Management Interface (DMI) table.

Command:

Bash

/usr/sbin/dmidecode | grep -A4 "System Information"
  • What it does: The -A4 flag tells grep to show the 4 lines after the match.
  • The Result: You will typically see:
    1. Manufacturer (e.g., Dell Inc., HP, Cisco)
    2. Product Name (e.g., PowerEdge R740)
    3. Version
    4. Serial Number
    5. UUID

🛠️ Method 3: The Modern ESXCLI Way

If you are on ESXi 6.x or 7.x/8.x, VMware has standardized most commands under the esxcli framework. This is often faster and cleaner than the legacy scripts.

Command:

Bash

esxcli hardware platform get
  • Why use this? It provides a clean, organized output of the Vendor Name, Product Name, and Serial Number without needing to grep.

⚠️ Troubleshooting Access

  1. SSH is Disabled: By default, SSH is turned off for security. You must enable it via the DCUI (the yellow and grey monitor screen) under “Troubleshooting Options” or via the Host Client web interface.
  2. Permission Denied: Ensure you are logging in as root. Standard users generally do not have permission to query the hardware DMI tables.
  3. Shell Lockdown: If the host is in “Lockdown Mode,” you will be unable to SSH in even with the correct credentials. You’ll need to disable Lockdown Mode via vCenter first.

#VMware #ESXi #SysAdmin #ITPro #CommandLine #ServerHardware #TechTips #LazyAdmin #DataCenter #RemoteManagement #vSphere

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ESXi Multipathing Decoded: MRU, Fixed, and Round Robin

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When you present a LUN to an ESXi host, the Native Multipathing (NMP) engine automatically assigns a policy based on the type of storage array detected. However, as an admin, you need to understand why a policy was chosen—and when you should manually intervene.

1. Most Recently Used (MRU)

Best For: Active/Passive Arrays. MRU selects the first working path it finds at boot. If that path fails, it switches to a standby path.

  • Key Behavior: It does not fail back. Even if the original path becomes healthy again, the host stays on the current path. This prevents “path thrashing” on Active/Passive arrays where switching controllers is an expensive operation.

2. Fixed

Best For: Active/Active Arrays. The Fixed policy uses a specific “Preferred Path.” If the preferred path fails, it moves to an alternative.

  • Key Behavior: It does fail back. As soon as that designated preferred path is back online, the host immediately switches back to it.

3. Round Robin (RR)

Best For: Load Balancing (Active/Active or ALUA). Round Robin rotates through all available paths to distribute the I/O load.

  • Active/Active: Uses every available path.
  • Active/Passive: Only uses all paths leading to the active controller.

Note: For Microsoft Failover Clusters (MSCS), Round Robin is only supported on ESXi 5.5 and later.

4. Fixed with Array Preference (FIXED_AP)

Introduced in ESXi 4.1 for ALUA-capable arrays, this policy lets the storage array tell the host which path is the “optimal” one.

  • Note: This was removed in ESXi 5.0 in favor of letting the NMP automatically select MRU or Fixed based on the array’s ALUA response.

⚠️ Critical Warnings for Admins

  1. Don’t Fight the NMP: VMware generally warns against manually changing a LUN from Fixed to MRU. The host chooses the policy based on the hardware it detects; forcing a change can lead to instability.
  2. Verify Vendor Support: Round Robin is powerful but not supported by every array. Always check the VMware Compatibility Guide before making it your default.
  3. MSCS Limitations: If you are virtualizing SQL clusters or other failover clusters, double-check your ESXi version before toggling Round Robin, or you risk losing disk heartbeat connectivity.

#VMware #ESXi #StorageAdmin #vSphere #Multipathing #SysAdmin #ITPro #Virtualization #LazyAdmin #DataCenter #StorageTips

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