Powercli

This is a quick one. Sometimes you need to evacuate VMs from a host, do some maintenance, and redistribute the VMs to the originating host. This can be annoying, especially if you don’t have a vSphere Enterprise Plus license with DRS, DRS groups etc. These few PowerShell lines may help you.

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TL;DR: There’s a script at the bottom of the page that fixes the issue.

Some days ago, this HPE customer advisory caught my attention:

Advisory: (Revision) VMware - HPE ProLiant Gen8 Servers running VMware ESXi 5.5 Patch 10, VMware ESXi 6.0 Patch 4, Or VMware ESXi 6.5 May Experience Purple Screen Of Death (PSOD): LINT1 Motherboard Interrupt

And there is also a corrosponding VMware KB article:

ESXi host fails with intermittent NMI PSOD on HP ProLiant Gen8 servers

Today, I had a very interesting discussion. As part of an ongoing troubleshooting process, console screenshots of virtual machines should be created.

The colleagues, who were working on the problem, already found a PowerCLI script that was able to create screenshots using the Managed Object Reference (MoRef). But unfortunately all they got were black screens and/ or login prompts. Latter were the reason why they were unable to run the script unattended. They used the Get-VMScreenshot script, which was written by Martin Pugh.

I’m not a developer. I deal mainly with infrastructe, things like virtualization, storage & backup, networking etc. Sometimes I had to write scripts, primarily PowerShell, batch or Bash. Many years back, I also wrote Csh and Ksh scripts. In the past years, automation was one of the rising trends in the infrastructure segment. And with automation, new challenges came up. Today I have to work with Windows PowerShell, in case of VMware with PowerCLI (which bases on Windows PowerShell), and sometimes I have use with REST APIs. I’m still not a developer. Due to this fact, I need tools that help me getting my work done.

Careful preparation is a key element to success. If you restart a storage controller, or even the whole storage, you should be very sure that all ESXi hosts have enough paths to every datstore. Sure, you can use the VMware vSphere C# client or the Web Client to check every host and every datastore. But if you have a large cluster with a dozen datastores and some Raw Device Mappings (RDMs), this can take a looooong time. Checking the path state of each LUN is a task, which can be perfectly automated. Get a list of all hosts, loop through every host and every LUN, output a list of all hosts with all LUNs and all paths for each LUN. Sounds easy, right?

DataCore describes in their Host Configuration Guide for VMware ESXi some settings that must be adjusted before storage from DataCore SANsymphony-V storage servers will be assigned to the ESXi hosts. Today, for ESXi 5.x and 6.0, you have to add a custom rule and adjust the advanced setting DiskMaxIOSize. For ESX(i) 4 more parameters had to be adjusted. But I will focus on  ESXi 5.x and 6.0. You need to adjust these settings for each host that should get storage mapped from a DataCore storage server. If you have more then one host, you may have the wish to automate the necessary steps. The check the current value of DiskMaxIOSize, you can use this lines of PowerCLI code.

Disk space is rare. I only have about 1 TB of SSD storage in my lab and I don’t like to waste too much of it. My hosts use NFS to connect to my Synology NAS, and even if I use the VAAI-NAS plugin, I use thin-provisioned disks only. Thin-provisioned disks tend to grow over time. If you copy a 1 GB file into a VM and you delete this file immediately, you will find that the VMDK is increased by 1 GB. This is caused by the guest filesystem. It marks the blocks of deleted files as free, even if it only deletes metadata and not the data itself. Later, the data is overwritten with new data, since the blocks are marked as free and the new data is written in there. VMware ESXi doesn’t know that the guest has marked blocks as free. So ESXi can’t shrink the thin-provisioned VMDK.

While preparing for a VMware vSphere 5.5 update at a customer of mine, I stumbled over VMware KB2085618 (ESXi host cannot initiate vMotion or enable services and reports the error: Heap globalCartel-1 already at its maximum size.Cannot expand.). I checked the HP AMS version in the latest HP custom ESXi image and found out, that version hp-ams-esx-550.10.0.0-18.1198610 is included (source). Unfortunately the bug is not fixed in 10.0.0, but it’s fixed in 10.0.1 (source).

Today I stumbled over a nice workaround. While installing a CentOS 6 VM, I needed to install the VMware Tools. I don’t know why, but I got an error message, regarding a non accessible VMware Tools ISO.

I remembered a blog post I read a few months ago, about a VMware online repository, from which VMware tools can be installed. You can download the repository information here. The RPM for RHEL can also be used for CentOS. Simply download and install the RPM:

Today I found this neat PowerCLI One-liner in my Twitter timeline:

PowerCLI Einzeiler um den Adapter-Typ einer VM auf Vmxnet3 zu ändern: Get-VM YOUR-VM |Get-NetworkAdapter |Set-NetworkAdapter -Type "Vmxnet3"

— T. Scheller (@bones44) February 28, 2014

A nice side effect of this one-liner is, that the mac-address doesn’t change, as you can see in the screenshots.