After a restore a virtual machine failed to start, the screen remained black and the following error was displayed: “Error loading operating system


All standard solutions like “chkdsk /r”, “chkdsk /p”, fixmbr, fixboot,… did not work.

After some deeper research I noticed that there may be a problem with the disk geometry of the virtual disk. I guess that this occured when we aligned a lot of virtual machines some times ago or something happend during the restore.

Fortunately I found a tool that helped to clean up the mess and made the virtual machine bootable.


  • Attach the broken boot disk (vmdk) to another virtual machine
  • download the tool “Testdisk
  • unzip the tool and start testdisk_win.exe on the virtual machine you use for repair

Select “No Log”:

Select the disk you want to repair:

Select “Intel/PC partition”:

Now select “MBR Code – Write TestDisk MBR code to first sector”:


  • confirm “Write a new copy of MBR code to first sector” with y (yes)
  • confirm “Write a new copy of MBR code, confirm” with y (yes)

Select OK after the new copy of MBR code has been written successfully.

Now select “Advanced – Filesystem Utils”:


In the next window select “Boot”:


If there are mismatches or problems you will get a view like this:


to solve this, select “Rebuild BS”

  • when the rebuild was successfull, leave the tool using “quit” till all windows are closed
  • unattach the virtual disk from the virtual machine
  • power on your broken Virtual machine – it should now boot without any problems!

This post is exceptionally not about virtualization – but maybe it is usefull for you in the near future…

My brother’s 8 GB SD card became unreadable/damaged as it was removed while there was read/write access to it.

From about 500 pictures of the last holiday only 20 were readable. When opening the other ones, the following errors came up:

  • Decode error! JPEG datastream contains no image!
  • Can’t open this picture because the file appears to be damaged, corrupted, or is too large

We tried checkdisk (chkdsk /F and chkdsk /r) and a lot of other free available data restore/recovery tools.

Most of them were not really free and you had to pay before you really knew if they can help you.

Finally I found a tool that helped us to restore all the photos (or nearly all… only ten out of 500 were definitely lost or garbled).

The name of the tool is Zero Assumption Digital Image Recovery (ZAR).

Generally the software is not free of charge, but the digital image recovery function of ZAR is available at no charge. And this function is the one we need :-)

You can download the software here: Download Zero Assumption Digital Image Recovery (ZAR)

After installation, open ZAR and select Image Recovery (Free):


In the next step select the broken SD Card Drive:


Now the software starts to analyse your SD card. Depending on the size this step can take some time/hours…


But it is worth to wait – because now you are only one step away to (hopefully) restore your data.

In the next window you can select the pictures/files ZAR found on your SD Card. Select all files you want to restore:


Now enter a path to restore and select “start copying the selected files”:


If you are lucky, most or all of your files are restored/reconstructed:


EMC_Booth_VMworldWhen visiting the Solutions Exchange at VMworld it was nearly impossible to miss the EMC booth.

They had an impressive exhibition booth, that was well visited, too.

This year they presented their EMC Hybrid Cloud solutions and products with a mini-theater session and cloud experts gave visitors a deep insight in personal discussions about eg:

Another topic was EMC XtremIO – an all-flash scale-out enterprise storage array.

EMC XtremIO is for example used in the VMware Hands-on-Labs datacenter in Amsterdam. A 12U EMC XtremeIO box replaced the previous used storage infrastructure solution that required five complete racks (this info came from a HOL architect during the VMUG HOL VIP Tour).

But EMC also supported community events at VMworld – this year for example they were so kind to be a sponsor of the vRockstar VMworld Kick-off party. The event took place in the Hard Rock Cafe at Sunday, October 12 and was a great success.


Another event at VMworld from EMC was the EMC TEEAM and Avnet Welcome Reception at Camp Nou inclusive a guided stadium tour. Thank you David (@SD_Cloudy) for the invitation!




During VMworld I took a closer look at software based virtual storage solutions.

In Solutions Exchange I’ve visited the booth of StarWind Software and they presented me their solution StarWind Virtual SAN.

StarWind Virtual SAN is available for both, VMware vSphere and Microsoft Hyper-V.

The installation is relatively easy. If you install it for vSphere, you need one Windows VM per ESXi host where you install the software. If you want to use it for Hyper-V you can install it directly on the Hyper-V host.

Vladan from has written an interesting post about how to “Install Free Starwind SAN on Free Hyper-V” – maybe you want to take a look at it.

Traditionally, Starwind Virtual SAN is used hyper-converged – means Virtual SAN is part of the hypervisor:


But it is also possible to separate compute and storage – a use case for this scenario would be, when there is need to grow by capacity only, eg. huge clustered Oracle or SQL Server deployments, scale-out file servers,…


At their website I have found some good technical papers dealing with the topic how to bild a StarWind Virtual SAN Hyper-Converged 2-Node Cluster with VMware vSphere respectively a 3-Node Cluster. If you read this you will get a good overview about installation and configuration.

Next I want to summarize some features:

Fault Tolerance and High Availability:

It’s up to you how many replicas of a LUN/VM you want to keep alive and how many active storage controllers a cluster should use. But whatever you choose, behind the scenes the software will create a fault tolerant shared storage using mirroring.

Scale-Up and Scale-Out possible:

Whether you want to add a new node with more ressources like RAM, CPU and storage (Scale-up) or you want to put more storage capacity in the existing node (Scale-Up) – both scenarios are possible.


It is possible to use RAM as a L1 cache. Using SSD is of course possible, too.

Deduplication, Compression and Thin Provisioning:

To increase usable capacity StarWind Virtual SAN allows in-line deduplication, compression and thin provisioning.

And much more like…

  • supports VAAI
  • NUMA aware resource management

Free Edition available:

There is a free version available, but of course there are some limitations. The free edition is limited to two servers with a 128 GB HA storage capacity. Asynchronous replication over WAN is also not possible, as well as no SPTI and NAS/SAN Cluster File Share.

If you want to know more about the free version you may be interested in the article: The difference between free and paid editions (pdf at

Please note:

This post is part of a series covering VMworld 2014. If you want to read more take a look at my VMworld 2014 page. If you think that there is something wrong (especially in the product takeaway posts) please let me know.