Joe Auty <j...@...> writes:

> 
> Any truth to this? The context here is my stating that I'm getting
> better performance out of Virtualbox in trying to trace down some I/O
> related performance issues with VMWare Server. I do not have the same
> I/O problems in Virtualbox, at least not in my limited testing. The
> difference is actually pretty dramatic.
> 
> > The problem with the comparison VirtualBox comparison is that caching
> > is known to be broken in VirtualBox (ignores cache flush, which, by
> > continuing to cache, can "speed up" IO at the expense of data
> > integrity or loss). This could be playing in your favor from a
> > performance perspective, but puts your data at risk. Disabling disk
> > caching altogether would be a bit hit on the Virtualbox side...
> > Neither solution is ideal.
> 

Hi,

this is not true for VBox 3.2 anymore if the host I/O cache is disabled and
SATA, SCSI or SAS is used. Flushes are passed to the disk by default in that
case.
If you want to pass cache flushes to the host for older VBox versions or IDE use

VBoxManage setextradata <VM name>
"VBoxInternal/Devices/piix3ide/0/LUN#0/Config/IgnoreFlush" 0

Flushes will then be passed to the file.

Regards,
Alexander Eichner



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