I have sbs 2008 virtual on 2 fixed VHD 1 x 100GB - 1 x 175GB on a 300GB HDD approx 4.5GB free. No snapshots. Every now and again(intermittently) the HDD holding the VHD's runs out of space and goes into paused-state critical. I managed to shutdown the machine, then restart and the space (4.5GB) returns, but I cannot see what causes it to grow in size? Any help appreciated
I think we need some more information before we can help.
What is installed on the host server, as from what you describe that is running out of space which is causing the hyper v machine to stop.
Are there any other hyper v machines that are running with expandable drives?
When you start your VM, Hyper-V will create a .bin file at your VM's location. This file is used for memory swapping and is as large as the amount of RAM assigned to the VM.
There are two ways of solving this:
1. Expand the physical storage or move the VM to a larger drive allowing the VM the grow (the better option)
2. Reduce the amount of RAM in the VM settings.
You could have unmerged snapshots in the background (they will not appear in the GUI but they exist). Search the file system for .AVHD files. The entire file system, all volumes.
Also, there is a Hyper-V specific section of the Event log - your details will be there. (it is outside System and Application in the MSFT section).
Backup agents that run within VMs are notorius for causing disks to grow with bunches of cache space that is later empty when you do your research. This can happen within the VM or at the storage level depending on how you do your backups.
Also, if you are using Dynamic VHDs, be mindful of the maximum size of the VHD - as the system is trying to grow it in 2Gb blocks in the background, up to the maximum size. You have to be careful that the maximum size is not larger than the storage volume can hold.
Also, when a VM is powered on a holding file that is equal to the amount of RAM of the VM is created. (you will find a .bin and a .vsv in the storage locaiton of the VM). If your VM has 4 Gb, this file is 4Gb. So you get extra space that is consumed. This file is a fail safe to make sure the system can pause the VM when something bad happens (like you run super low on disk space).
Brian Ehlert (hopefully you have found this useful) http://ITProctology.blogspot.com
Where do I find this .bin file?
I have sbs 2008 virtual on 2 fixed VHD 1 x 100GB - 1 x 175GB on a 300GB HDD approx 4.5GB free.
These are NOT dynamic VHD's.
There are no snapshots involved.
The Host machine is not running out of space, the drive that holds the VHD's is running out of space due to the VHD increasing in size yet it is set to static?
For more information about bin file, you can refer to:
Understanding where your virtual machine files are [Hyper-V]
I found the reason why the disk is running out space but not sure why? Then Host machine Windows 2008 had a "System Volume Information" folder on the same drive as the folder which holds the VHD files, within this folder there was a system file which grew and made the disk run out of space. I checked the drive and shadow copies is disabled on the drive but there was used space. Within the settings button I moved the max size down to 300MB, OK out of the GUI, then check the properties of the drive and the used space was zero and the file disappeared from the "System Volume Information" folder. Not sure what caused this as shadow copies are disabled?