Huihong Luo wrote:
No problem. Can you shed some lights on why writing to vhd is so much slower
than to vmdk? Considering that these two are so similar in layout. Only diff is
the bitmap on VHD
Don't have time to do an in-depth investigation, but the bitmap is
certainly the prime suspect. The bitmap is not cached (VMDK has a block
mapping cache, and VDI has the entire block map in memory, just like
VHD). For VHD, each write operation first reads the corresponding bitmap
entry, and if the bitmap is updated then there is an additional write as
well. This case is triggered a lot for writes to a new VHD image.
Windows is certainly not famous for its file cache efficiency.
Hope this gives a few hints what to tweak to get better performance.
Klaus
Sent from my iPhone
On Oct 15, 2009, at 4:24 AM, Klaus Espenlaub <klaus.espenl...@sun.com> wrote:
Huihong Luo wrote:
found another bug, I've attached the patch
two bugs:
(1) parent locators set to zero for base images
(2) block allocation table to be block-size aligned (2M)
after these two fixes, vbox vhds works well on Hyper-V, I tested quite some
large vhd files from p2v, all works fine now.
These two fixes should be very safe to check in, (not sure if it may break
snapshots, though)
Thanks a lot for those fixes (and the previous ones as well), I'll try to find
time myself to apply them in the near future - or find someone else who will
handle it.
What I wanted to ask earlier already - did you read
http://www.virtualbox.org/wiki/Contributor_information ? Which of the two
contribution options (SCA or MIT licensed patches) do you pick?
Again, we're very grateful for the excellent contributions.
Klaus
- hl
--- On *Tue, 10/13/09, Huihong Luo /<huisi...@yahoo.com>/* wrote:
From: Huihong Luo <huisi...@yahoo.com>
Subject: Re: [vbox-dev] Fwd: VHD not readable by Hyper-V
To: "vbox-dev@virtualbox.org" <vbox-dev@virtualbox.org>
Date: Tuesday, October 13, 2009, 1:40 PM
I found the vhd bug on vbox implementation. vbox mistakenly sets
parent locators ("wi2r", etc.) for base vhd image. If setting these
fields to zeros for base image, Hyper-V is happy. Should be very
easy to fix, if you need the code diff, let me know
VBox The MS spec states:
Parent Locator Entries
These entries store an absolute byte offset in the file where the
parent locator for a differencing hard disk is stored. This field is
used only for differencing disks and should be set to zero for
dynamic disks.
--- On *Tue, 10/13/09, Huihong Luo /<huisi...@yahoo.com>/* wrote:
From: Huihong Luo <huisi...@yahoo.com>
Subject: [vbox-dev] Fwd: VHD not readable by Hyper-V
To: "vbox-dev@virtualbox.org" <vbox-dev@virtualbox.org>
Date: Tuesday, October 13, 2009, 6:49 AM
Sent from my iPhone
Begin forwarded message:
*From:* Huihong Luo <huisi...@yahoo.com>
*Date:* October 13, 2009 6:35:42 AM PDT
*To:* Shu Wu <superwu...@gmail.com>
*Subject:* *Re: [vbox-dev] VHD not readable by Hyper-V*
No problem with vpc, vbox also understands vhds from hyper-v
It is just that hyper-v doesn't understand vbox's vhd
Sent from my iPhone
On Oct 13, 2009, at 2:27 AM, Shu Wu <superwu...@gmail.com> wrote:
Can your VHD disk be read by Virtual PC or Virtual Server? It
seems that Hyper-V and Virtual-PC share the same vhd format.
One year ago I wrote my own program to generate a vhd file
and make it to be accepted by Virtual PC, just following the
official vhd specification. But I haven't tested it on Hyper-V.
Cheers,
Wu Shu
2009/10/13 Klaus Espenlaub <klaus.espenl...@sun.com>
Huihong Luo wrote:
None of vbox created vhd disk files are readable by
2008 Hyper-V.
This is the error: "The file or directory is
corrupted and unreadable"
I am debugging through the code, trying to change
Footer info, such as version, creator OS, checksun,
etc., to see it can correct the error.
If you know what might be wrong, pls post
We only know what Microsoft documents in their VHD format
spec, which we believe to have correctly implemented.
However as usual those specs are incomplete and not
really precise, so there's plenty of room for different
interpretations.
Klaus
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