Can't fill a hard drive? Error "Could not power on VM : No space left on device."

[GregBradley]

My server has local storage. 4 146Gb 10k drives RAID5 for files and 3 73Gb 15k drives RAID5 for data. So my data drive is only 136.5GB with 3 73GB drives. I would like to make that one virtual machine and use the drive space for one Win2003x64 VM. When I try to configure a machine with all the drive space, it gives me an error saying it is too large before it tries to create the VM.

If I drop it to 135Gb and use 256Mb RAM for my Win2003x64 machine, it will let me configure it and start the machine.

If I use my desired 4096MB RAM I have to drop it to 134GB it will allow the VM to be created but I get the above error when trying to start it.

If I drop it to 130GB it will create and start.

So my big question is: If I have to leave some of the storage on that drive for ESXi, how much do I need for best performance? A better question is "why doesn't ESXi know how much space it needs when you are configuring the drive size?"

[ascari · Accepted solution]

Hi Greg,

when you create a VM, you need space for yous *-flat.vmdk files but remember: you need space for:

Configuration file (.vmx) - hd descriptor files (.vmdk) - VM bios file (.nvram) - VM log files (.log) - vm swap file (.vswp) - eventually snapshot files.

If you not have some free disk space you can not power on your vm or if it's already powered on it's will stop.

For ... how many free space... ; it's not a good idea working with your free space disk very low. Really, if you have only space for virtual disk, swap, and logs, your vm can working, but if you need to do a normally snap for vcb, your vm will stop working.

I hope to have been useful.

Bye Alberto

[fejf]

Hi,

first there is the metadata which is created on each vmfs (size depending on the block size - lets say around 500mb). If you want to power on a VM then the VMKernel creates a temporary file with the size of the ram of the VM. This means if you set the RAM of a VM to 4GB and you want to power on the VM the .vswp file will be 4GB. It will be smaller if you use memory reservation (but this may have other disadvantages). That means that the maximum size of your vmdk will be around 136,5GB - 4,5GB = 132GB. This can be less because there are also config files etc and as already said the metadata size varies.

--

There are 10 types of people. Those who understand binary and the rest. And those who understand gray-code.

[Dave_Mishchenko]

Here's a good thread to read through regarding disk space and the various files ESX creates http://communities.vmware.com/message/649338. If you plan to use snapshots for backups then you'll want to ensure there is free space for that. However, you do have the option to specific another location for the swap file so that would give you an extra 4 GB to use.

[GregBradley]

So much to learn about virtual that is SO different from real.

Guess you guys have convinced me to just add more 10k drives and save the faster drives for another system.