Hey Marko im having a similar problem with that too. I'm using server 2012 r2 though. I found that running anything on the 2k12 vm is massively slow because of c drive disk queue length. Yo can see the disk performance through system performance monitor. Anything over 1 for disk queue length is bad - I've been seeing anywhere from 5 to 50. If I run a 2008r2 vm on the same host it's fine. I haven't tried downgrading the hardware yet but what version is your vm at? there is another thread that states downgrading the hw to v10 or v9 will resolve the issue.

You can can email me at adam.savage@monster.com

Here are some resolution but it's not a VMware's official one.

Windows Server 2012 or above can support In-Guest unmap and trim.

That function cause a problem with VMware's new In-Guest unmap support.

This function works well under Hyper-V environment but doesn't works well with VMware's one.

01. Use a VM Hardware verwion 10 (ESXi 5.5 compatible) that doesn't support In-Guest unmap.

      If you downgrade VM hardware version 10 you will escape from high disk usage.

      But you can't never use In-Guest unmap function.

02. Use fsutil command in Windows Guest OS - Windows Server 2012 or above -

     In Windows command shell with administrative right then execute belows.

     These commands will disable Windows In-Guest unmap and trim on NTFS, ReFS v1, v2.

     -- disable unmap and trim on NTFS & ReFS v1

     fsutil behavior set DisableDeleteNotify NTFS 1

     -- disable unmap and trim on ReFS v2

     fsutil behavior set DisableDeleteNotify ReFS 1

     If you want to rollback to Windows unmap function execute belows

     fsutil behavior set DisableDeleteNotify NTFS 0

     fsutil behavior set DisableDeleteNotify ReFS 0

Plus ~

If you disable In-Guest unmap but you can unmap on VMFS with vmfstools command manually...:)

Best Regard,

Jaehoon Choi

You are my hero!

New vSphere 6.5 Update 1 released.

ESXi 6.5 update 1, too!

I'm test theses release then check out that VMware resolve this issues...:)

Best Regard,

JaeHoon Choi

I installed this update using a script, rebooted the server, but the problem remained.

esxcli software profile update -p ESXi-6.5.0-20170304001-standard -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml

Only the disabling of these modes in the system really saves the situation.

You have installed wrong Version ?

ESXi-6.5.0-20170304001-standard

From VMWare Site 6.5 U1 = ESXi-6.5.0-20170701001-standard

Greet

Sven Grimm

Has anyone confirmed if this update contains the fix and if it does, in fact, work properly after upgrading?

Can confirm that patched to latest 6.5.0 has improved speeds from 20-30mb/s read to 250mb/s read. Just updated via ISO and bootable media for easy life.

Thanks for all the help of those who re-assured it was just something that needed patching.

patch to esxi 6.5d or 6.5 update 1?

Sorry Colin,

VMware-VMvisor-Installer-6.5.0.update01-5969303.x86_64.iso

So update 1.

I have the same problem. Windows Server 2016 is very very slow on esxi 6.5d. Hope it's been fixed by 6.5 update1.

Thank you for your  reply.

I ran into this issue last few days.  Very sluggish 99% guest disk activity on local SSD datastore.   Experienced both Server16 + Win10 guests...Disabling unmap in guest fixed it.

Just updated Dell T610 with VMware-VMvisor-Installer-6.5.0.update01-5969303.x86_64-DellEMC_Customized-A00.iso

Re-enabled guests unmap.  Tested.  6.5 U1 fixed it.

Good news. Thanks for taking the test and share the result.