Solutions Log » Virtualization

Honor Guest IDE/SATA Flush Requests

Dan — Mon, 07 Dec 2009 20:43:59 +0000

Issue:
VirtualBox ignores IDE/SATA disk flush requests.

Cause:
This is by design. To improve performance VirtualBox ignores these requests. This can create an issue with filesystems that do not have fsck-like tools (ZFS is an example) create a situation where the on disk information is inconsistent due to data held in RAM.

Solution:
To enable flushing for IDE disks, issue the following command:

VBoxManage setextradata VMNAME
"VBoxInternal/Devices/piix3ide/0/LUN#[x]/Config/IgnoreFlush" 0

The value [x] that selects the disk is 0 for the master device on the first channel, 1 for the slave device on the first channel, 2 for the master device on the second channel or 3 for the master device on the second channel.

To enable flushing for SATA disks, issue the following command:

VBoxManage setextradata VMNAME
"VBoxInternal/Devices/ahci/0/LUN#[x]/Config/IgnoreFlush" 0

The value [x] that selects the disk can be a value between 0 and 29.

Reference: http://www.virtualbox.org/manual/UserManual.html#id2499944

Shrink VirtualBox vdisks After Freeing Space (Windows guests)

Dan — Thu, 13 Aug 2009 19:35:47 +0000

Issue:
On dynamically allocated vdisks, freed space on a guest is never released back to the host once freed.

Cause:
This is by design.

Resolution:
The procedure for shrinking (compacting in VirtualBox parlance) is straightforward and consists of a series of steps.

Delete files on the guest to achieve the desired amount of free space
Zero free space out with an appropriate utility
Shut down guest
Compact disk

Zeroing guest free space is simple: Microsoft provides an excellent utility through its Sysinternals group called SDelete. Download the program, extract it from the archive, and execute it on the disk to be zeroed. Note: this procedure only zeroes free space.

sdelete -c

One the zeroing procedure is completed, you may power off the guest and compact the virtual disk from the command line.

VBoxManage modifyvdi /path/to/machine.vdi compact

Note: This was tested against VirtualBox 3.0.4 r50677

References:
SDelete

Install VMware Tools on a Gentoo Guest

Dan — Wed, 08 Jul 2009 16:21:01 +0000

emerge pciutils mkinitrd
mkdir /etc/rc.d
cd /etc/rc.d
for i in `seq 0 6`; do mkdir rc$i.d; done
File -> Install VMware Tools
mount /mnt/cdrom
cd /tmp
tar xvfz /mnt/cdrom/VMwareTools-3.5.0-158874.tar.gz
cd vmware-tools-distrib/
./vmware-install.pl
All defaults with the exception of:
/etc/rc.d -> location of the rc.d directories
/etc/init.d -> location of the init scripts
When prompted to run vmware-tools-config, decline
rc-update add vmware-tools default
/usr/bin/vmware-config-tools.pl
Verify that everything compiles without error
Reboot
Verify that VMware tools are reported as running in the VI console

Note: This was tested and found working under VMware VI 3.5.x with Gentoo x86_64, kernel 2.6.27-gentoo-r8.

Where to score xVM Guest Additions

Dan — Mon, 06 Jul 2009 16:08:22 +0000

A simple google search for "xVM Guest Additions" will yield a few links. As of 6 July 2009, Sun has made available an early access version of the additions.

It may be found here.

Change the UUID of a VirtualBox vdi disk file

Dan — Wed, 13 May 2009 14:27:46 +0000

You use the VBoxManage command with the clonehd argument.

VBoxManage clonehd