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Archive for the ‘Virtualization’ Category

Converting a virtual IDE disk to a virtual SCSI disk (1016192)

Posted by jpluimers on 2020/09/11

Just in case I have a VM with only IDE disks of which one ore more need to become SCSI disks: [WayBack] Converting a virtual IDE disk to a virtual SCSI disk (1016192)


  1. Add one SCSI disk
  2. Install drivers for it and get it recognised
  3. When the VM is shutdown:
    1. Modify the disk description of the IDE disk to SCSI (hack) or
    2. (often easier) remove the disk, then attach it to the SCSI controller


Posted in Power User, VMware, VMware ESXi, Virtualization | Leave a Comment »

ESXi: shrinking a thin provisioned disk by first exploding it with zero content

Posted by jpluimers on 2020/09/07

In addition to ESXi: shrinking a Windows disk, you can shrink any ESXi thin provisioned disk by first exploding it with zero content, then shrinking it like described by [WayBack] How to Shrink a Thin VMDK on ESXi 5.0 | Boerlowie’s Blog.

It comes down to using this command:

 vmkfstools --punchzero myVirtualMachineDisk.vmdk

You can replace --punchzero with -K if you like more cryptic arguments.

This works because thin provisioned vmdk disk files are sparse files where zero content can be non-allocated.

The trick requires all empty space to be zeroed out (which usually comes down using a tool like sdelete on Windows or shred on Linux), hence the “exploding” in the post title.

For a good explanation on thin, versus thick versus eagerlyZeroedThick, read [WayBackThin Provisioning – What’s the scoop? – VMware vSphere Blog.

A few remarks:

  • this only works within datastores, so when you transfer your file out, then the file will be the thick size
  • an OVF exported virtual machine will benefit from thin provisioned disks
  • the du command will show the actual storage size (including the savings from think provisioned disks)
  • the ls command will show then “virtual” storage size (excluding any thin provisioning gains)
  • the difference between ls and du output is the thin provisioning gain


Posted in Power User, Virtualization, VMware, VMware ESXi | Leave a Comment »

ESXi: shrinking a Windows disk

Posted by jpluimers on 2020/09/04

I had to shrink down a Windows disk of an ESXi based Virtual Machine from 240 Gibibyte to about 140 gigabyte.

In this case, it was Windows 7 on ESXi 6.5, but the actual versions do not really matter.

The only way to decrease ESXi .vmdk files is by fiddling with disk sector counts in the text based .vmdk files (not the binaries .vmdk files!) of a diskname.vmdk / diskname-flat.vmdk text/binary pair. This is described for instance in these two articles:


  1. This article presumes you already shrunk your NTFS partition (for instance as described in Consolidating NTFS free space).
  2. If you only have a binary .vmdk file, then you can use vmkfstools to create a text/binary pair for you, for instance by using these commands:
    vmkfstools --clonevirtualdisk Windows7.vmdk Windows7.thick.vmdk
    vmkfstools --clonevirtualdisk Windows7.vmdk Windows7.thin.vmdk --diskformat thin
  3. You cannot workaround 2. as the --geometry functionality of vmkfstools only displays existing geometry, see

ESXi has .vmdk files that count disk sizes in sectors, but the tooling that ship with Windows to not show partition sizes in sectors, especially not the partition ending sector.

All permutations of tooling like DISKPART, PowerShell, WMIC and terms partition, ending sector, cylinder, head, etc failed me to return built-in tools.

Luckily, “powershell” “partition” “ending sector” found the documentation for [WayBack] Test Disk | File System | Data Management titled “TestDisk Documentation, Release 7.1, Christophe GRENIER” which lead to:

[WayBack] TestDisk Download – CGSecurity

Download TestDisk & PhotoRec. TestDisk is a free and open source data recovery software tool designed to recover lost partition and unerase deleted files. PhotoRec is a file carver data recovery software tool.

It is available for many platforms, including Windows x86 (fully featured) and x64 (limited features):

There was also the much more convoluted PowerForensics which is also more difficult to install:

As a check (because the calculations by hand are too cumbersome to trust on a first trey), I also downloaded the ISO image of gparted:

Let’s get started for real!

Read the rest of this entry »

Posted in Power User, Virtualization, VMware, VMware ESXi, Windows, Windows 7 | Leave a Comment »

HOW TO: Configure Shared Diagnostic Partition on VMware ESX host |

Posted by jpluimers on 2020/08/31

Interesting for vSphere clusters: [WayBack] HOW TO: Configure Shared Diagnostic Partition on VMware ESX host |


Posted in Power User, Virtualization, VMware, VMware ESXi | Leave a Comment »

VMware ESXi 6.5: “Failed – An error occurred during host configuration.” when starting the NTP service

Posted by jpluimers on 2020/08/10

I tried repeating VMware KB: Configuring Network Time Protocol (NTP) on ESX/ESXi hosts using the vSphere Client in ESXi 6.5 using the web-client (the steps are very similar, see [WayBack] How to configure ESXi 6.5 Network Time Protocol (NTP) via Host Client? | ESX Virtualization).

It failed with the non-descriptive “Failed – An error occurred during host configuration.”:

Viewing the details isn’t of much help as you do not get extra information:

Read the rest of this entry »

Posted in ESXi6.5, Power User, Virtualization, VMware, VMware ESXi | Leave a Comment »

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