[Solved] Performance influence of VHD size

[petrusalberts2@gmail.com]

Hi

I use VirtualBox to run Microsoft 2016 Server for MS Dynamics 365 F&O development. So I know the basics, but not a lot. After every MS release I download a new VHD file. This file seems to have a fixed size.

Recently I had to use terminal to increase a VHD size (the VM didn't have any space left). Now I am wondering what the performance benefit is to increase the VHD size? I know a shortage of disc space can slow a PC down, so I assume it will also be the case with a VM?

Thanks for your attention

[mpack]

I know a shortage of disc space can slow a PC down, so I assume it will also be the case with a VM?

As you say, disk congestion can have a negative affect on performance. The nature of the disk drive makes no difference to that.

[socratis]

After every MS release I download a new VHD file.

What does that mean? Where do you download a "new VHD file" from? And do you build a new VM around it?

This file seems to have a fixed size.

Then you can't resize it. That's what "fixed" means...

[petrusalberts2@gmail.com]

Hi sorry for the late reply.

What does that mean?

Not sure - I think from LCS. When MS releases a new version of D365 F&O they will either provide a script to update existing VM's or supply a new version that can be downloaded. Some technical guy in my organisation handles that - every now and then I will receive a new VHD file (physically given to me on an external drive - I copy it onto my PC). For example I had a VM FinanceAndOperationsV10PU27.vhd which I recently discarded when I received FinanceAndOperationsV10PU29.vhd

And yes then I will build a VM around the VHD. I follow the steps in the new VM wizard and then do a few basic configurations, such as network adaptors (for RDP and internet), processor count and paravirtualization.

Then you can't resize it. That's what "fixed" means...

lol... Well I need extra space. I open terminal and use the

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vboxmanage modifymedium F&OV10.vhd --size 9999999999

I am not sure how much extra disk space is useful. My current VM is 105GB with 22GB of free space. Firstly I have a vague idea that a server shouldn't be running with only 100GB of disk space (regardless of available space) and also that it will perform better with more than 20GB of free space. But then I don't have tons of time to test and observe. That is the reason for the post I was hoping a professional here could give me some insight. Thanks again for the responses!

[mpack]

Are you running applications on the server which traditionally require lots of disk space? If not then 20GB free seems fine to me.

"Server" is a role: it provides services to callers. It says nothing about resource requirements. The precise role you want it to play tells you that.

[petrusalberts2@gmail.com]

That makes sense, thanks.

I am just interested in performance. Things that take up my time are Visual Studio (the D365 add-in is resource intensive), IIS restarts (after a build it takes ages for the IIS to get back up again) and SQL in general (some extra DB speed will be welcome). I think those are applications that require (or could benefit from) lots of disk space?

I realise now (because you mentioned), that disk congestion on a VM is not different from disc congestion on a PC. So then this post is not really so relevant to this forum

[mpack]

It sounds like the best change you can make, if you haven't already done it, is to host the VM on an SSD.

Adding more disk capacity as such when you already have plenty will not speed things up, likewise adding more CPU cores can slow the VM down, if the extra cores aren't actually being used, so don't make that mistake either. The general rule is to share resources equitably between guest and host, smooth running of both is needed since they share the work.

[petrusalberts2@gmail.com]

Thank you very much. You and Socratis have been very helpful.

I have the information I need. Should I do something to mark this post as "closed" or "answered"? I do not see any options.

[mpack]

You just edit the title, but I have done it for you.

[socratis]

I missed the afternoon chat, but one thing that struck me as "odd", was the command that you used to attempt to resize the VHD:

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vboxmanage modifymedium F&OV10.vhd --size 9999999999

That seems wrong in so many levels...

• First of all, the filename, "F&OV10.vhd", that "&" seems out of place, not sure if it's even valid.
• Second, if the virtual hard disk (the VHD) is the fixed-size kind (which you said it was), then the command would have failed.
• Third (and most important), you shouldn't just throw values randomly. If the command was successful, then your virtual hard disk would have a logical size of 9,999,999,999 MB = 9,765,625 GB = 9,536.7 TB = 9,31 PB. That's almost 10 petabytes! You definitely don't want that...