Category Archives: Uncategorized

CVE-2020-16875 Exchange Memory corruption vulnerability

Last week Microsoft released a Security Update for Exchange 2019 (CU5 and CU6) and Exchange 2016 (CU16 and CU17) that addresses the CVE-2020-16875 vulnerability.

It is recommended to test this update in your lab environment quickly and deploy them in production when no issues are found.

Download locations and KB articles can be found on my page under the Exchange 2019 or Exchange 2016 section.

Windows Server 2016 Hyper-V quickly fills up system disk

Recently I had to replace my two lab servers, so I bought two brand new HP DL360-Gen9 servers. Lots of memory and a number of disks and processor capacity. Two weeks after installing Windows 2016 Hyper-V I noticed that my system disk (C:\ drive, approx. 185 GB) was filling up rapidly.


Initially I thougt it was the paging file (with 192 GB internal memory this can be an issue) but this was not the case since the paging file was located on drive D:\

Further investigation revealed that most data was located in the directory C:\ProgramData\Microsoft\Windows\Hyper-V\Virtual Machines, where all VM related files are located (except the virtual hard disks which were located in D:\Hyper-V\Virtual Hard Disks). It turned out to be very dynamic data located in .VMRS file. When a VM was turned off the VMRS file was gone, as soon as the VM was turned on again dir VMRS file was allocated again, and the size of the file was identical to the amount of memory of the Virtual Machine as can be seen in the following screenshot:


Next I’ve been looking at the smart paging option in Hyper-V, but this only makes sense when using dynamic memory, which was not the case in my environment (VMs were running Exchange 2013/2016).

Production snapshots are new in Windows 2016 Hyper-V. Production snapshots use VSS to create a snapshot (where the traditional snapshots create a system state using .VSV and .BIN files) so that would make sense in my scenario. But disabling snapshots at all on a VM basis didn’t make any difference, and the .VMRS files were still created.

The last option I had was the Automatic Stop Action option in Hyper-V (on a per VM basis). Using this option you can control what happens when the host shuts down. By default it is set to Save the virtual machine state, so when the Hyper-V host shuts down the entire VM is saved at that particular moment. To achieve this, space on disk is reserved equal to the amount of memory used by VM. Other options here are Turn off the virtual machine and Shut down the guest operating system.


Bingo, this was my issue. Save state will certainly have performance benefits, but I prefer to use the shut down option in my lab environment. After changing this on (most of) my VMs I have plenty of free space on my system disk Glimlach

Enable File History in Windows 8.1

This blog post is more a ‘note to self’, but for my work I write a lot of documents and a proper backup of my documents is key for me. The last thing I want to happen is a crash of my hard disk and lose valuable data. So, at home I have a Synology NAS (with 5 disks in RAID-5) and I want to store backups on this device.

To configure File History (which let you create backups) open Control Panel, select System and Security and select File History. File History is disabled by default:


Continue reading Enable File History in Windows 8.1

Upgrade Lync 2013 to Skype for Business 2015 Step-by-Step

Now that Microsoft has released Skype for Business 2015 it’s time to have a look at the upgrade possibilities. I’m running Lync 2013 Standard Edition in my environment (Lync 2013 Front-End Server, Lync 2013 Edge server and Lync 2013 Mediation server), and lucky enough there is an in-place upgrade possibility. A downtime if required, but when scheduling off business hours this should not be a problem. In this blog post I’ll discuss a step-by-step upgrade from Lync 2013 Standard edition to Skype for Business 2015.


Before the servers can be upgraded to Skype for Business 2015 a number of requirements need to be met, depending of the underlying Operating System:

  • Microsoft Lync Server 2013 CU5 (February 2015 update) or above
  • PowerShell RTM version (6.2.9200.0) or later
  • SQL Server 2012 SP1 or later
  • Kb2533623 Windows Server 2008 R2
  • Kb2858668 Windows Server 2012
  • KB2982006 Windows Server 2012 R2

I’m running Windows Server 2012 R2 on all my servers, so the only updates I have to apply is the Cumulative Update for Lync (to be safe, the May 2015 Cumulative Update ( and the SQL Server 2012 SP1 update.

Continue reading Upgrade Lync 2013 to Skype for Business 2015 Step-by-Step

Free Kemp LoadMaster

Kemp recently released a free version of their virtual LoadMaster (VLM) load balancer solution. It is just like a regular VLM with some restrictions of course. There’s no High Availability support in the free LoadMaster, there’s only web-based support and you cannot update the firmware to a newer version for example. Also the bandwidth is limited to 20Mbit (L7) throughput with 50 transactions (TPS) 2K SSL keys.

However, it does support the nice features such as Global Server load balancing, the Application Firewall Pack and the Edge Security Pack. This makes it a perfect solution for small organizations, for lab environment or for regular test environments. It is possible though to upgrade the free LoadMaster to a regular device, making it also a perfect solution for a Proof-of-Concept. When finished the POC you an easily bring the LoadMaster to production by upgrading the license.

Continue reading Free Kemp LoadMaster