I'm trying to plan disk space for a virtual environment, and wanting to keep virtual disks as small as possible - mostly as apart from the base OS, the software going onto the VM is less than a few MB, so want to avoid physical disk space going to waste; plus it'll give me an idea of how many VMs I could physically fit in {x}GB of physical drive.

For Server 2003, I've had installs on 2GB and 5GB sized virtual disks. However for Server 2008, Microsoft recommends a minimum of 10GB (I assume this is both for x32 and x64). For the record, I will be installing the x32 version.

Now I know I could just go ahead and try a small install, but wanted to solicit any practical knowledge as well :-) What's the smallest install of Server 2008 possible? (excluding server core installations).

Target virtualisation environment: Microsoft Hyper-V
Target use: development/peertest environment, so it's likely that we'll be creating and tearing down servers on a semi-regular basis. Lifetime of a single VM may vary from a day or so to over a year.


I would agree that 40 GB would be the minimum C: partition. I prefer 50 GB.

The reason for this is the escalating disk usage of the Windows side-by-side folder (%systemroot%\Winsxs). This is currently 10 GB on my R1 server, and it continues to grow over time. I would allocate 20 GB just for this folder for the lifetime of the server.

  • I'm reading up on it now. I haven't really tracked it before as previously it's all been physical boxes. I tend to clamp down heavily on VMs and would rather a VM only takes the resources it needs: hosting a 30GB+ VM to host an app that only takes a few MB just seems an horrendous waste of disk. Thankfully I don't have to guest 2k8 with a commercial hosting environment - I guess 2k8 just isn't cut out for it; disk often isn't cheap and one chap's already been caught out: serverfault.com/questions/79485/… – Chris J May 5 '10 at 13:03

The smallest footprint you can install server 2008 x32 is 1.5 GB (using server core) Paging files will use more space. That being said would you like to run applications? If your apps really only use up a few MB of disk space then a 5-15 MB disk partition should be fine. As a person that's done commericial hosting with windows, disk size is generally the last thing to worry about. When you virtualize, the amount of IOPS required for the shared storage usually provides more than enough space for all of the VMs.

Whiel Hyper-v doesn't have thin provisioning, but you can use differencing disks to save space between various builds (1 parent base OS disk and any number of application disks), so that naother option would be to go ahead and give windows 30 Gb and give the apps each their own differencing disks

  • Using dynamically expending disks will also save your physical disk space. It's not as fast as fixed sized VHDs, but if spance is the amin concern... You can also compact them on a regular basis to be sure you're using as little disk space as possible. – Chris S May 5 '10 at 15:02
  • yes you can use dynamic disks at hte expense of increased iops however if you're already thta short on space it's likely you are already overcommited on disk – Jim B May 5 '10 at 16:49

What's your planned hypervisor and/or storage? i.e. can you not just use thin-provisioning?

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    See edits. On the thin-provisioning, we've got a couple of standalone servers; no SAN at the back, so not sure this is possible. Will investigate though. – Chris J May 5 '10 at 11:20
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    I think you're right, I'm pretty sure HV doesn't have 'thin' support - have you thought of using the free version of ESXi for this? – Chopper3 May 5 '10 at 11:25

You can install and run with 20GB for a while but you will run into trouble after a year or so as the remnants of patching and other crud starts to accumulate, and it will accumulate. I would strongly recommend that you do not go smaller than the 40GB that Microsoft recommend, I'd personally push that to 50GB (+ page file if you are putting the page file on the system volume).

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    Good grief - cheers though: food for thought. I'm starting to loathe the amount of disk space you need for all the "hidden" things that MS tries to keep track of. By comparison, Server 2003 runs quite happily in a tiny footprint... – Chris J May 5 '10 at 11:22

I'd go for a 40 or 60 GB partition utilizing thin provisioning, and turn off swap (if you can hand enough memory to the server), or at least attach a second 8GB partition that is only for swap.

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