Thursday, March 14, 2019

How to transfer large ISO files to ESXi Datastore with USB disk?

I'm participating in one VMware virtualization PoC and we had a need to transfer large ISO file to VMFS datastore on standalone ESXi host. Normally you would upload ISO files over the network but PoC network was only 100Mbps so we would like to use USB disk to transfer ISOs to ESXi host.

There is William Lam blog post "Copying files from a USB (FAT32 or NTFS) device to ESXi" describing how you can use USB with FAT or NTFS filesystem to transfer ISOs but it did not work for me, therefore I wanted to use VMFS filesystem for ISO files transfer. I have VMware Fusion on my MacOSX laptop so it is very easy to spin up VM with ESXi 6.7 and have network access (local within a laptop) to ESXi. I use USB stick connected to the laptop and passed through to VM with ESXi. USB disk is recognized by ESXi but the only challenge is to create VMFS datastore because web management (HTML5 Client) does not allow create new VMFS datastore on USB disks.

Som, the only way is to create it from the command line.

By the way, all credits go to the blog post "Creating A VMFS Datastore On A USB Drive" and here is a quick installation procedure based on the mentioned blog post.

STOP USB Arbitrator

/etc/init.d/usbarbitrator status
/etc/init.d/usbarbitrator stop
/etc/init.d/usbarbitrator status

Find USB disk name

vdq -q
esxcfg-scsidevs -l

echo $MYDISK

Create 10GB VMFS datastore on USB disk

partedUtil getptbl $MYDISK
partedUtil mklabel $MYDISK gpt
partedUtil showGuids
partedUtil setptbl $MYDISK gpt "1 2048 20000000 AA31E02A400F11DB9590000C2911D1B8 0"
vmkfstools -C vmfs6 -S E2USB-ISO-Datastore ${MYDISK}:1

So datastore E2USB-ISO-Datastore is created and you can use upload ISO files to datastore and it goes over the virtual network within laptop computer so it is pretty fast.

Datastore usage on real ESXi host

When ISO files are on USB datastore, you can gracefully shutdown virtual ESXi, remove USB disk from a laptop and connect it to physical ESXi system. USB Arbitrator on physical ESXi system must be temporarily disabled by command ...

/etc/init.d/usbarbitrator stop 

... otherwise, the disk would not be usable within ESXi host as a USB device would be ready for USB passthrough, which you do not want in this particular case. After data transfer to non USB datastore, you can remove USB disk and start USB arbitrator ...

/etc/init.d/usbarbitrator start 

Hope this procedure helps at least one other person in VMware virtual community.

What motherboard chipset is used in VMware Virtual Hardware?

Today I have been asked by one of my customers what motherboard chipset is used in VMware Virtual Hardware. The answer is clearly visible from the screenshot below ...

Motherboard chipset

Motherboard chpset is Intel 440BX ( This chipset was released by Intel in April 1998. In the same year, VMware Inc. was founded.

The screenshot above was done in Windows 10 running as Guest OS in VM hardware version 13 but the same chipset is used for VM hardware version 14 so I would assume all VM hardware versions use the same chipset and difference among VM hardware versions are additional features like the maximum amount of RAM, number of NIC adapters, CPU features exposed from physical CPU to virtual CPU, etc.

On two pictures below you can see VM hardware difference between ESXi 3.5 and ESXi 4.0

ESXi 4.0

ESXi 3.5

Friday, March 01, 2019

VMware vSphere Memory Hot Add scalability limitation

VMware vSphere Hot Add CPU/Memory feature has specific requirements and limits. To mention some
  • Virtual machines minimum hardware is version 7.
  • It is not compatible with Fault Tolerance
  • vSphere Enterprise Plus license
  • Hot Remove is not supported
  • Hot-Add/Hot-plug must be supported by the Guest operating system (check at
  • Guest-OS technical and licensing limitations had to be taken into consideration.
However, it is good to know about another scalability limitation.

VMware has set a maximum value for hot add memory. By default, this value is 16 times the amount of memory assigned to the virtual machine. For example, if the virtual machine memory is 2 GB, the maximum value for hot add memory is 32GB (2x16).

Actually, this is a good safety mechanism and here is the reason for such restriction ...

When hot memory is enabled, the guest operating system uses a huge amount of kernel memory space in the PFN database. Windows operating system does not have dynamic PFN allocation. When adding memory to the virtual machine, to make it visible to the guest operating system, the PFN database needs to be dynamic as Windows lacks this feature.

Do you want to know more about "Page Frame Number (PFN) database"? Read this article.

This topic is documented in VMware KB

Now there is another question. Does this limitation apply only to MS Windows or it applies to Linux OS as well? The short answer is yes it applies to Linux as well. However, for Linux OS there is another limitation. If you are running WM with Linux OS having less then 3GB RAM you can change the memory only up to 3GB RAM in total. If you need more. You have to power off VM, increase memory to for example 4 GB RAM and power on again. When you are running linux with more than 3GB you can use hot memory add but again with a limit to increasing it maximally 16 times.

Hope this is informative.

Memory Hot Add related VMware KBs: