VSAN 5.5 – A general system error occured: Inappropriate ioctl for device

So recently I was building a Microsoft DFS server for use on our VDI Infrastructure. I built the server from my company template and proceeded to put on file services, setup shares, etc and then I realised that I hadn’t expanded the Data disk beyond the 100GB default. Given that I needed 1.5 TB for this particular share, I thought to myself “No problem, quick login to vSphere Web and expand the disk, VSAN size limit at 5.5 is 2TB(-512b) – right!?

As I was increasing the size of the disk, I saw the following error:

“A general system error occured: Inappropriate ioctl for device”.


This was odd and a quick Google search didn’t return much, so I checked some logs on: The VM, ESXi Host and vCenter. The only pointer that I was able to find was in the vCenter vpxd log which highlighted the same error that I had seen but gave me a “Generic VM” settings error. Nothing really concrete to go on. At this stage, I went back to good old troubleshooting basics and tried the following:

– Power down the VM and tried to increase (Failed, same error).
– Increase disk using host direct vSphere client (Failed, same error).
– Increase disk using VMKFSTOOLS on the host (Failed, same error).
– vMotion the VM to another host in the VSAN cluster and try again (Failed, same error).
– Create a new VM from the same template and test disk increase on that (Failed, same error).
– Created a new iSCSI adapter and moved the disk to that (Failed, same error).
– Checked all the HW versions and tools, all fine.
– Tried creating new disks on the VM’s to ensure there wasn’t a problem with the template (This functionality was fine).

Not wanting to give up but also getting annoyed that I was starting to waste far too much time on a simple task, I tried increasing the disk from 100GB to 200GB (before this stage I had been increasing from 100GB to 1500GB each attempt, because – why shouldn’t I, right?). Low and behold, the increase worked?! So I tried:

– 200GB to 1500GB (Failed, same error).
– 200GB to 500GB (Worked)
– 500GB to 1500TB (Failed, same error).
– 500GB to 900GB (Worked).
– 900GB to 1500TB (Failed, same error).
– 900GB to 1100GB (Worked).
– 900GB to 1500GB (Worked).


Strangely enough, it appeared that I wasn’t able to increase the VMDK on the VSAN file system in one single large increment, I had to increase it in stages! I was able to create a brand new disk of 1500GB but that isn’t what I wanted because I’d already setup my shares and done some work which would have been annoying to reproduce.

A very wierd issue that I have never seen before. It would be good to investigate at a later point in time, I am able to recreate the problem so might raise an GSR to get to the bottom of it. I’m perhaps wondering if it has something to do with the fact that my VSAN host disks are made up of 400GB SSD and 1TB HDD’s.

I hope this helps someone if they encounter the same issue!


  1. Erik Verbruggen

    I’ve tried to see of this issue also exists in VSAN 6.1 and it does not. In our lab environment we are also using 1TB HDD’s so i tried the same as you did. An existing 100GB VMDK, resized to 1500GB, and it completed successfully.

    • Ryan Harris
      Ryan Harris

      Hi Erik,

      Thanks for the comment and getting involved. Interesting to see you aren’t getting this issue in 6.0 U1. My environment is going to be upgraded next weekend so I think I’ll keep an eye on the situation and see if the problem is resolved once the upgrade is complete. For now I have worked around it and I can’t see this being an issue moving forward, even if the work wasn’t going ahead next weekend!

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