Hi folks

sometimes when running VM's - especially as servers (nothing wrong in using a VM as a server) you will considerably improve I/O throughput if you use the native file system for the OS instead of using Virtual HDD's.

For instance if you run Windows Guests on a Linux host in the classical way with virtual HDD's the I/O has to handle both the vm hdd and the Windows file handler (ntfs-3g in Linux --which mounts the fuse (windows ntfs handler) in the kernel).

Similarly for Linux guests running on Windows hosts .

Attaching external HDD's to the VM is no problem as these can be attached with native file systems in the usual way.

The problem is with internal HDD's.

You need to allocate the WHOLE disk and in the VM setup specify it as a RAW HDD. That way Windows etc won't complain if it sees an HDD with a foreign file system on it or ask you to re-format it every time you re-boot the HOST system.

On the Guest just handle the HDD in the usual way e.g if Linux guest just mount the device or with Windows the HDD should be recognized as soon as the VM is powered on.

This should beef up your I/O on VM's quite considerably. Note use this for DATA. Keep the guest OS itself on a Virtual disk - and an SSD is the best place for this.

The 3 main sets of Vm software people use on these forums (VMware, vbox and Hyper-V) all allow for RAW HDD pass through to the guest.

If you can run the VM on an SSD (the OS part) then so much the better too.