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VSICM55 - Slide 03-13 - Virtual Disk



1. Room for improvement:

The virtual machine virtual disk maximum configurable size has changed in vSphere 5.5 and the slide doesn't mention it at all.

1. Source:

VMware vSphere 5.5 Configuration Maximums.

1. Info:

According to the "vSphere Virtual Machine Administration" guide - "Configuring Virtual Machine Hardware in the vSphere Web Client" chapter - "Virtual Disk Configuration" paragraph - "Large Capacity Virtual Disk Conditions and Limitations" topic, here is what you shall know about virtual disks larger than 2TB:

  • The maximum value for large capacity hard disks is 62TB.
  • The guest operating system must support large capacity virtual hard disks.
  • You can move or clone disks that are greater than 2TB to ESXi 5.5 or later hosts or to clusters that have such hosts available.
  • The datastore format must be VMFS5 or later or an NFS volume on a Network Attached Storage (NAS) server.
  • Virtual Flash Read Cache supports a maximum hard disk size of 16TBs.
  • VMFS3 volumes are not supported. You cannot move disks greater than 2TB from a VMFS5 datastore to a VMFS3 datastore.
  • You cannot hot-extend virtual SATA disks, or any virtual disk if the capacity after extension is equal to or greater than 2TB.
  • Fault Tolerance is not supported.
  • Virtual SAN is not supported.
  • BusLogic Parallel controllers are not supported.
1. Source:

VMware vSphere 5.5 Documentation Center.



2. Room for improvement:

Starting with vSphere 5.5, virtual machines have a new type of virtual storage adapter: SATA AHCI (Advanced Host Controller Interface).

2. Source:

What's New in VMware vSphere 5.5 Platform technical white paper.

2. Info:

The "vSphere Virtual Machine Administration" guide - "Configuring Virtual Machine Hardware in the vSphere Web Client" chapter - "SCSI and SATA Storage Controller Conditions, Limitations, and Compatibility" paragraph offers more information.

Each virtual machine can have a maximum of four SCSI controllers and four SATA controllers.
When you create a virtual machine, the default controller is optimized for best performance. The controller type depends on the guest operating system, the device type, and in some cases, the virtual machine's compatibility. For example, when you create virtual machines with Apple Mac OS X guests and ESXi 5.5 and later compatibility, the default controller type for both the hard disk and the CD/DVD drive is SATA. When you create virtual machines with Windows Vista and later guests, a SCSI controller is the default for the hard disk and a SATA controller is the default for the CD/DVD drive.
If you add a SATA controller, you can reassign an existing or new hard disk or device to that controller. For example, you can assign the device to (1:z ), where 1 is SATA controller 1 and z is a virtual device node from 0 to 29. For SATA controllers, you can use device nodes 0 through 29, including 0:7.

Last sentence, referring to device node 0:7, stating it can be used to allocate virtual disks to a SATA controller, is opposed to SCSI controllers where node 0:7 is by default assigned to the virtual SCSI controller itself.

2. Source:

VMware vSphere 5.5 Documentation Center.



3. Room for improvement:

Last sentence in slide notes refers to independent disks and their two options, persistent and non-persistent, yet it doesn't provide any description about the behavior of those disks.

3. Info:

The "vSphere Virtual Machine Administration" guide - "Configuring Virtual Machine Hardware in the vSphere Web Client" chapter - "Virtual Disk Configuration" paragraph - "Change the Virtual Disk Configuration in the vSphere Web Client" topic provides some more details.

  • Independent Persistent Disks: disks in persistent mode behave like conventional disks on your physical computer. All data written to a disk in persistent mode are written permanently to the disk.
  • Independent Non-persistent Disks: Changes to disks in non-persistent mode are discarded when you turn off or reset the virtual machine. With non-persistent mode, you can restart the virtual machine with a virtual disk in the same state every time. Changes to the disk are written to and read from a redo log file that is deleted when you turn off or reset the virtual machine.
3. Source:

VMware vSphere 5.5 Documentation Center.


Last modified onTuesday, 17 December 2013 19:20
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