VCP6-DCV blueprint section 3:Configure and Administer Advanced vSphere 6.x Storage -Objective 3.4 – Part 2 and Objective 3.5

Home / blueprint / VCP6-DCV blueprint section 3:Configure and Administer Advanced vSphere 6.x Storage -Objective 3.4 – Part 2 and Objective 3.5

In this post we will continue covering the storage objective from the blueprint.

The following are the blueprint objective:


  • Differentiate NFS 3.x and 4.1 capabilities
  • Connect an NFS 4.1 datastore using Kerberos


  • Differentiate Physical Mode RDMs and Virtual Mode RDMs
  • Create a Virtual/Physical Mode RDM
  • Configure Bus Sharing
  • Configure Multi-writer locking

SIOC: (i skipped some parts of the blue print because i didn’t study the marital yet such as “Differentiate between SIOC and Dynamic Queue Depth Throttling features”)

  • Describe the benefits of SIOC
  • Enable and configure SIOC
  • Configure/Manage SIOC
  • Monitor SIOC


NFSv3 and NFS4.1:

VMware support both NFS protocols here are the differences between the two:


  • Traffic is unencrypted
  • Use only one TCP connection for I/O.
  • ESXi has No support for delegate user functionality
  • Supports hardware acceleration and integration with NAS devices
  • Locking on ESXi does not use the Network Lock Manager (NLM) protocol (use VMware locking)


  • Support multipathing for servers that support session trunking, use of multiple IP addresses to access a single NFS volume
  • Does not support hardware acceleration.
  • Supports the Kerberos authentication protocol to secure communication with the NFS server.
  • Uses share reservations as a locking mechanism, and have build in file locking(no need for VMware locking
  • supports nonroot users to access files when used with Kerberos


Not all VMware features currently support by NFSv4 , THIS WILL CHANGE WITH FUTURE VERSIONS!!!

Source: VMware vSphere Storage document



Connect an NFS 4.1 datastore using Kerberos:


  • ESXi Hosts need to be part of the Active directory
  • Need to configure user that have credentials to authenticate with the kerberos server



I included only the screenshots that are different from NFSv3:








An RDM is a mapping file in a separate VMFS volume that acts as a proxy for a raw physical storage device. The RDM allows a virtual machine to directly access and use the storage device. The RDM contains
metadata for managing and redirecting disk access to the physical device.


Source: VMware vSphere Storage document


There are two modes of RDM :physical and virtual 

Physical Mode: Allows the guest operating system to access the hardware directly. Physical compatibility is useful if you are using SAN-aware applications on the virtual machine. However, a virtual machine with a physical
compatibility RDM cannot be cloned, made into a template, or migrated if the migration involves copying the disk.

Virtual Mode: Allows the RDM to behave as if it were a virtual disk, so you can use such features as taking snapshots, cloning, and so on. When you clone the disk or make a template out of it, the contents of the LUN are copied into a .vmdk virtual disk file. When you migrate a virtual compatibility mode RDM, you can migrate the mapping file or copy the contents of the LUN into a virtual disk.


Create a Virtual/Physical Mode RDM:

Before I add a new RDM drive in my lab i will need to create more LUNs in my Windows server and than i need to re-scan for the new disk


On the vm setting click on new device >> RDM disk and click add.n


Choose the new LUN and click Ok.


Choose physical or virtual RDM:


Configure Bus Sharing and Configure Multi-writer locking:

Bus Sharing: Under the SCSI controller section you can configure SCSI Bus Sharing


Multi-Writer: under Sharing you can configure Multi-writer


Storage I/O Control


Describe the benefits of SIOC:

Storage I/O control its like QOS for your datastore , you can control the amount of I/O per VM during period of I/O congestion.When you enable SIOC the ESXi host start to monitor the latency and when a latency threshold reached SIOC allocate resource in proportion of their shares.

Enable and configure SIOC:

by default SIOC is disabled to enable SIOC on a datastore: Click on the datastore >> Manage>>Setting >> General >> Edit

You can configure % peak throughput  or adjusted to manual when you can actually control the latency.


Once SIOC is enable you will be able to configure the Shares and I/O limits for a specific VM,


To monitor SIOC resource allocation (Shares and Limits) go to Datastore >> Related Objects>> Virtual Machines.


Thanks for reading



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