Hi Brian, On Sunday 08 March 2009, Brian J. Murrell wrote: > > * Check the disk settings in the guest: Does the guest drive the > > hard disk in DMA mode or PIO mode? > > Hrm. How do I determine that from Windows XP?
Open the device manager and right click on the IDE controller channel 0. You should find a page where the transfer mode is shown. > > The Session Information shows: > DMA Transfers 492,884 > PIO Transfers 59,770 > Data Read 5,062,400,000 B > Data Written 2,773,438,000B Hmm, som PIO transfers but much more DMA transfers. I assume the count of the PIO transfers does not increases during the benchmark, does it? > > * Which benchmark did you use for measuring the throughput? > > Something called DiskTT.exe. It doesn't look terribly "scientific" but > I ran it a number of times to ensure consistency at least and it was > consistent enough on both VBox and native hardware to at least some > somewhat trustworthy. If we were niggling about 10-20% difference > between the two I would be more concerned but we are talking about a > factor of 4 or more. > > So what about host CPU? On a dual core system, is VBox able to take > advantage of both cores if necessary? While top shows the VM pegged at > 100% all of the time, sar shows that that most of the time a single core > is not pegged but usually a combination of load on each, such as (there > is much disk access during this as I rsync from C: to an F: which is a > VDI: VBox should definitely make use of multiple cores. Although it supports only one guest CPU, intensive I/O will benefit from multiple cores as most devices have dedicated worker threads. The ATA controller has two worker threads, one for the primary channel and one for secondary channel. When is one CPU pegged at 100%? The whole time or only during the benchmark? Kind regards, Frank -- Dr.-Ing. Frank Mehnert Sun Microsystems http://www.sun.com/
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