yes, it's on windows, but it may perform similar on Linux too. As Klaus pointed out in previous emails, it's more likely to do with the bitmap. Block size might be a factor too. If you examine vhdWrite(), it does the following: (1) read bitmap (1 sector) (2) write block (3) write footer (4) write the bitmap this is 4 disk i/o, and especially, (3) - > (4) repositions the disk head back, very expensive Huihong
--- On Mon, 10/19/09, Frank Mehnert <frank.mehn...@sun.com> wrote: From: Frank Mehnert <frank.mehn...@sun.com> Subject: Re: [vbox-dev] writing to VHD/VDI is 50% slower of VMDK? To: vbox-dev@virtualbox.org Date: Monday, October 19, 2009, 3:15 AM On Tuesday 13 October 2009, Huihong Luo wrote: > This seems to be always the case, writing a large amount of data to vdi/vhd > is much much slower than writing to a vmdk disk. > I am using the the vboxddu.dll code, and clone physical disk to virtual > disk. > for example, clone 250G takes about 2.50 hrs to a vmdk file, whereas it > takes 4 hrs to a vdi file, under exact conditions, quite reproducible. > There is only writes to disks, no reads. So this is a Windows host, correct? I can't imagine the reason for such a slowdown as there are not many differences between the backends. One differnece between .vmdk and .vdi is the block size. This needs further investigation. Kind regards, Frank -- Dr.-Ing. Frank Mehnert Sun Microsystems, Inc. www.sun.com -----Inline Attachment Follows----- _______________________________________________ vbox-dev mailing list vbox-dev@virtualbox.org http://vbox.innotek.de/mailman/listinfo/vbox-dev
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