Assign priority tags to traffic, such as VoIP and streaming video, that has higher networking requirements for bandwidth, low latency, and so on. You can mark the traffic with a CoS tag in Layer 2 of the network protocol stack or with a DSCP tag in Layer 3.

1. Locate a distributed port group or an uplink port group in the vSphere Web Client.
   1. Select a distributed switch and click the Related Objects tab.
   2. Click Distributed Port Groups to see the list of distributed port groups, or click Uplink Port Groups to see the list of uplink port groups.
2. Right-click the port group and select Edit settings.
3. Select Traffic filtering and marking.
4. If traffic filtering and marking is disabled, enable it from the Status drop-down menu.
5. Click New to create a new rule, or select a rule and click Edit to edit it.
6. In the network traffic rule dialog box, select the Tag option from the Action drop-down menu.
7. Set the priority tag for the traffic within the scope of the rule

Specify the kind of traffic that the rule is applicable to.

1. From the Traffic direction drop-down menu, select whether the traffic must be ingress, egress, or both so that the rule recognizes it as matching.

   The direction also influences how you are going to identify the traffic source and destination.

2. By using qualifiers for system data type, Layer 2 packet attributes, and Layer 3 packet attributes set the properties that packets must have to match the rule.

   A qualifier represents a set of matching criteria related to a networking layer. You can match traffic to system data type, Layer 2 traffic properties, and Layer 3 traffic properties. You can use the qualifier for a specific networking layer or can combine qualifiers to match packets more precisely.

   • Use the system traffic qualifier to match packets to the type of virtual infrastructure data that is flowing through the ports of the group . For example, you can select NFS for data transfers to network storage.
   • Use the MAC traffic qualifier to match packets by MAC address, VLAN ID, and next level protocol.

     Locating traffic with a VLAN ID on a distributed port group works with Virtual Guest Tagging (VGT). To match traffic to VLAN ID if Virtual Switch Tagging (VST) is active, use a rule on an uplink port group or uplink port.

   • Use the IP traffic qualifier to match packets by IP version, IP address, and next level protocol and port.
   • In the rule dialog box, click OK to save the rule.

Voice over IP (VoIP) flows have special requirements for QoS in terms of low loss and delay. The traffic related to the Session Initiation Protocol (SIP) for VoIP usually has a DSCP tag equal to 26, which stands for Assured Forwarding Class 3 with Low Drop Probability (AF31).

For example, to mark outgoing SIP UDP packets to a subnet 192.168.2.0/24, you can use the following rule:

https://kb.vmware.com/s/article/1009554

https://kb.vmware.com/s/article/1009555

Sometime we see Backup failed for that VM with the error message :

Virtual disk configuration change detected, resetting CBT failed Details: A general system error occurred: 
Creating VM snapshot
Error: A general system error occurred: 

There are few documents which you can find for this error .I couldn’t reboot the host as this was a production cluster. After some homework, i figured out some ways to fix the issue.

1: Reboot the Virtual Machine.

This task will refresh the .vmx file and you will get your VM in a healthy state back again.

2: If this happens there is no guarantee that you will be able to recover the VM. So better have an older backup ready, and recover the Virtual machine.

3: The virtual machine’s .vmx configuration file can be reloaded from the command line. This operation does not generate a new Inventory ID (Vmid) for the virtual machine and allows it to stay in the same resource pool.

To resolve this issue, reload the virtual machine’s .vmx configuration file.

To reload the virtual machine’s .vmx configuration file, perform one of these options:

• Reload the configuration file of all the virtual machines on the ESXi/ESX host using a script by running this command:for a in $(vim-cmd vmsvc/getallvms 2>&1 |grep invalid |awk ‘{print $4}’|cut -d \’ -f2);do vim-cmd vmsvc/reload $a;done
  • Reload the .vmx configuration file from the command line:

  1. Log in to the Local Tech Support Mode console of the ESXi/ESX host.
  2. Obtain the Inventory ID (Vmid) for the virtual machine using this command:# vim-cmd vmsvc/getallvms

     Note: The output shows virtual machines which are registered on the ESXi/ESX host.

     You see output similar to:

     Vmid Name File Guest OS Version Annotation
2848 Test.vmx winNetEnterpriseGuest vmx-07 To be used as a template

     In this example, the Vmid is 2848.

  3. Reload the .vmx file using this command:# vim-cmd vmsvc/reload Vmid

  Either of the steps should work to fix the issue.

UEFI Secure Boot is a security standard that helps ensure that your PC boots using only software that is trusted by the PC manufacturer. For certain virtual machine hardware versions and operating systems, you can enable secure boot just as you can for a physical machine.

1. Browse to the virtual machine in the vSphere Client inventory.
2. Right-click the virtual machine and select Edit Settings.
3. Click the VM Options tab, and expand Boot Options.
4. Under Boot Options, ensure that firmware is set to EFI.
5. Select your task.
   • Select the Secure Boot check box to enable secure boot.
   • Deselect the Secure Boot check box to disable secure boot.
6. Click OK.

If you plan to set up and use an iSCSI LUN as the boot device for your host, follow certain general guidelines.

If this issue occurs, the VMFS volume (and the virtual machines residing on the affected volume) are unavailable to the ESX/ESXi host.

Use the vmkfstools command to break the device lock on a particular partition.

When entering the device parameter, use the following format:

You can use this command when a host fails in the middle of a datastore operation, such as expand the datastore, add an extent, or resignature. When you run this command, make sure that no other host is holding the lock.

1. To break the lock:
   1. Break the existing LVM lock on the datastore by running this command:

      # vmkfstools –B vmfs device

      Note: You can also use the parameter –breaklock instead of -B with the vmkfstools command.

      From the preceding error message, this command is used:

      # vmkfstools -B /vmfs/devices/disks/naa.60060160b3c018009bd1e02f725fdd11:1

      You see output similar to:

      VMware ESX Question:
      LVM lock on device /vmfs/devices/disks/naa.60060160b3c018009bd1e02f725fdd11:1 will be forcibly broken. Please consult vmkfstools or ESX documentation to understand the consequences of this.

      Please ensure that multiple servers aren’t accessing this device.

      Continue to break lock?
      0) Yes
      1) No

      Please choose a number [0-1]:

   2. Enter 0 to break the lock.
   3. Re-read and reload VMFS datastore metadata to memory by running this command:

      # vmkfstools –V

   4. From the vSphere UI, refresh the Storage Datastores View under Configuration tab.

Note: This issue can also be resolved by restarting all the hosts in the cluster.

Use the vmkfstools command to reserve a SCSI LUN for exclusive use by the ESXi host. You can also release a reservation so that other hosts can access the LUN, and reset a reservation, forcing all reservations from the target to be released.

-L|–lock [reserve|release|lunreset|targetreset|busreset|readkeys|readresv] device

Caution:Using the -L option can interrupt the operations of other servers on a SAN. Use the -L option only when troubleshooting clustering setups.

Unless advised by VMware, never use this option on a LUN hosting a VMFS volume.

You can specify the -L option in several ways:

• -L reserve – Reserves the specified LUN. After the reservation, only the server that reserved that LUN can access it. If other servers attempt to access that LUN, a reservation error appears.
• -L release – Releases the reservation on the specified LUN. Other servers can access the LUN again.
• -L lunreset – Resets the specified LUN by clearing any reservation on the LUN and making the LUN available to all servers again. The reset does not affect any of the other LUNs on the device. If another LUN on the device is reserved, it remains reserved.
• -L targetreset – Resets the entire target. The reset clears any reservations on all the LUNs associated with that target and makes the LUNs available to all servers again.
• -L busreset – Resets all accessible targets on the bus. The reset clears any reservation on all the LUNs accessible through the bus and makes them available to all servers again.
• -L readkeys – Reads the reservation keys registered with a LUN. Applies to SCSI-III persistent group reservation functionality.
• -L readresv – Reads the reservation state on a LUN. Applies to SCSI-III persistent group reservation functionality.

When entering the device parameter, use the following format:

ESXi supports the unmap commands issued directly from a guest operating system to reclaim storage space. The level of support and requirements depend on the type of datastore where your virtual machine resides.

Inside a virtual machine, storage space is freed when, for example, you delete files on the thin virtual disk. The guest operating system notifies VMFS about freed space by sending the unmap command. The unmap command sent from the guest operating system releases space within the VMFS datastore. The command then proceeds to the array, so that the array can reclaim the freed blocks of space.