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google上关于vmware的一些问题的讨论
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Message 1 in thread
寄件者：Bin Chen ([email protected])
主旨：About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-21 17:30:06 PST
Hello,
Now I want write some infomation into a vmware virtual disk file,but I
found that the format of the virtual disk file is not the same as a
real disk.For example ,the fist 512 bytes of the file is not the mbr
or boot sector!
So I am curious about the format of the virtual disk.
Any help appreciated!
Best Regards,
Chen Bin
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Message 2 in thread
寄件者：Tuukka Toivonen ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-22 00:15:06 PST
In article <[email protected]>, Bin Chen wrote:
> Now I want write some infomation into a vmware virtual disk file,but I
> found that the format of the virtual disk file is not the same as a
> real disk.For example ,the fist 512 bytes of the file is not the mbr
I would guess that it has some header, after which is the raw data. Could
you try looking for the MBR in the rest of the bytes?
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Message 3 in thread
寄件者：Kasper Dupont ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-22 01:37:46 PST
Tuukka Toivonen wrote:
>
> I would guess that it has some header, after which is the raw data. Could
> you try looking for the MBR in the rest of the bytes?
It is not that simple. Some other emulators use a virtual disk in that
format. DOSEMU has a 128 byte header, and all PC emulators I have seen
for Amiga used another format with a 512 byte header.
But VMware is more complicated. In fact initially the VMware diskfile
is smaller than the emulated disk, but I guess it will have to grow as
data gets written to the disk.
--
Kasper Dupont -- der bruger for meget tid p? usenet.
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Message 4 in thread
寄件者：M?ns Rullg?rd ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-22 03:06:31 PST
Kasper Dupont writes:
> > I would guess that it has some header, after which is the raw data. Could
> > you try looking for the MBR in the rest of the bytes?
>
> It is not that simple. Some other emulators use a virtual disk in that
> format. DOSEMU has a 128 byte header, and all PC emulators I have seen
> for Amiga used another format with a 512 byte header.
>
> But VMware is more complicated. In fact initially the VMware diskfile
> is smaller than the emulated disk, but I guess it will have to grow as
> data gets written to the disk.
VMware uses some copy-on-write mechanism, similar to the VM in most
OSes. There must be something equivalent to a page table somewhere in
the file, most likely near the start. Has anyone tried asking for
specs on the file format?
--
M?ns Rullg?rd
[email protected]
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Message 5 in thread
寄件者：Kasper Dupont ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-22 04:33:49 PST
M?ns Rullg?rd wrote:
>
> VMware uses some copy-on-write mechanism, similar to the VM in most
> OSes. There must be something equivalent to a page table somewhere in
> the file, most likely near the start.
I looked on a VMware file once, and the start of the file did look
like some kind of tables, so I guess you are right about that.
> Has anyone tried asking for specs on the file format?
Yes, Bin Chen just did that. But I guess you mean has anyone tried
asking the authors of VMware about the format. I have not tried.
--
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Message 6 in thread
寄件者：Robert Kaiser ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-22 02:15:48 PST
In article ,
Tuukka Toivonen writes:
> In article <[email protected]>, Bin Chen wrote:
>> Now I want write some infomation into a vmware virtual disk file,but I
>> found that the format of the virtual disk file is not the same as a
>> real disk.For example ,the fist 512 bytes of the file is not the mbr
>
> I would guess that it has some header, after which is the raw data. Could
> you try looking for the MBR in the rest of the bytes?
It's not _that_ simple. I looked into this once (but not very deeply).
It looks as if it somehow skips unused blocks in the "disk". And it may
also compress data. For instance, I have a virtual disk which Win98 says
is 1.94 GB, 898 MB used, but the corresponding Linux file is only ~711 MB.
Rob
--
Robert Kaiser email: rkaiser AT sysgo DOT de
SYSGO AG http://www.elinos.com
Klein-Winternheim / Germany http://www.sysgo.de
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Message 7 in thread
寄件者：Bin Chen ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-22 18:28:14 PST
[email protected] (Robert Kaiser) wrote in message news:...
> In article ,
> Tuukka Toivonen writes:
> > In article <[email protected]>, Bin Chen wrote:
> >> Now I want write some infomation into a vmware virtual disk file,but I
> >> found that the format of the virtual disk file is not the same as a
> >> real disk.For example ,the fist 512 bytes of the file is not the mbr
> >
> > I would guess that it has some header, after which is the raw data. Could
> > you try looking for the MBR in the rest of the bytes?
>
> It's not _that_ simple. I looked into this once (but not very deeply).
> It looks as if it somehow skips unused blocks in the "disk". And it may
> also compress data. For instance, I have a virtual disk which Win98 says
> is 1.94 GB, 898 MB used, but the corresponding Linux file is only ~711 MB.
>
> Rob
If the machanism of VM disk file is the same as described above,I will
be very disappointed about VMWare.
Are there any other good X86 emulator that can be easily extended by
user?
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Message 8 in thread
寄件者：Richard Pitt ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-22 23:55:13 PST
On Fri, 22 Nov 2002 18:28:13 -0800, Bin Chen wrote:
> [email protected] (Robert Kaiser) wrote in message
> news:...
>> In article ,
>> Tuukka Toivonen writes:
>> > In article <[email protected]>, Bin
>> > Chen wrote:
>> >> Now I want write some infomation into a vmware virtual disk file,but
>> >> I found that the format of the virtual disk file is not the same as
>> >> a real disk.For example ,the fist 512 bytes of the file is not the
>> >> mbr
>> >
>> > I would guess that it has some header, after which is the raw data.
>> > Could you try looking for the MBR in the rest of the bytes?
>>
>> It's not _that_ simple. I looked into this once (but not very deeply).
>> It looks as if it somehow skips unused blocks in the "disk". And it may
>> also compress data. For instance, I have a virtual disk which Win98
>> says is 1.94 GB, 898 MB used, but the corresponding Linux file is only
>> ~711 MB.
>>
>> Rob
>
> If the machanism of VM disk file is the same as described above,I will
> be very disappointed about VMWare.
>
> Are there any other good X86 emulator that can be easily extended by
> user?
has anyone else ever dealt with a "sparse" disk?
blocks which contain all "null" blocks don't take up 'real' space.
richard
--
Richard C. Pitt C.E.O. Belcarra Technologies
[email protected] direct: 604-644-9265 www.belcarra.com
Software Systems - design and implementation: Internet, Linux, Communications
USB, RNDIS, ATM, E-mail, SQL, Encryption, Security, Web, Embedded Systems
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Message 9 in thread
寄件者：M?ns Rullg?rd ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 06:06:32 PST
Richard Pitt writes:
> has anyone else ever dealt with a "sparse" disk?
>
> blocks which contain all "null" blocks don't take up 'real' space.
That's not exactly right. Blocks that have never been written to
don't use any disk space. They do read as zeros. If anything, even
zeros, is written to them there will be physical space allocated.
--
M?ns Rullg?rd
[email protected]
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Message 10 in thread
寄件者：Kasper Dupont ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 06:27:11 PST
M?ns Rullg?rd wrote:
>
> Richard Pitt writes:
>
> > has anyone else ever dealt with a "sparse" disk?
> >
> > blocks which contain all "null" blocks don't take up 'real' space.
>
> That's not exactly right. Blocks that have never been written to
> don't use any disk space. They do read as zeros. If anything, even
> zeros, is written to them there will be physical space allocated.
Why does VMware implement that? I think it could just rely on
sparse files implemented by the underlying filesystem.
--
Kasper Dupont -- der bruger for meget tid p? usenet.
For sending spam use mailto:[email protected]
char *mybuf[1==1]; (2==3)[mybuf]="Hello World!";
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Message 11 in thread
寄件者：M?ns Rullg?rd ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 09:26:18 PST
Kasper Dupont writes:
> > > has anyone else ever dealt with a "sparse" disk?
> > >
> > > blocks which contain all "null" blocks don't take up 'real' space.
> >
> > That's not exactly right. Blocks that have never been written to
> > don't use any disk space. They do read as zeros. If anything, even
> > zeros, is written to them there will be physical space allocated.
>
> Why does VMware implement that? I think it could just rely on
> sparse files implemented by the underlying filesystem.
I was talking about sparse file in Linux (and most Unixes). VMWare
probably duplicates the functionality because VMWare is also available
for Windows, and Windows doesn't have sparse files. I guess the
virtual disk format is the same in the windows and linux versions of
VMWare and that would be the reason for not using sparse files on
linux. As usual we all have to suffer from the drawbacks of windows,
even if we don't use it ourselves.
--
M?ns Rullg?rd
[email protected]
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Message 12 in thread
寄件者：Bruce Stephens ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 06:22:35 PST
[email protected] (Bin Chen) writes:
[...]
> Are there any other good X86 emulator that can be easily extended by
> user?
VMware isn't an emulator, it's a virtualizer. Bochs is an emulator
(and so will run on non-ix86 hardware, which VMware won't). plex86
is a project to develop
an open source virtualizer, but I don't know that it works yet.
valgrind also includes an x86 emulator; a performance comparison
between valgrind and bochs might be interesting.
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Message 13 in thread
寄件者：Kasper Dupont ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 14:23:24 PST
Bruce Stephens wrote:
>
> [email protected] (Bin Chen) writes:
>
> [...]
>
> > Are there any other good X86 emulator that can be easily extended by
> > user?
>
> VMware isn't an emulator, it's a virtualizer.
Why do you say it is not an emulator? Isn't a virtualizer just an
emulator taking advantage of large similarities between the host
architecture and the emulated architecture?
--
Kasper Dupont -- der bruger for meget tid p? usenet.
For sending spam use mailto:[email protected]
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Message 14 in thread
寄件者：Bruce Stephens ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 17:17:51 PST
Kasper Dupont writes:
> Bruce Stephens wrote:
>>
>> [email protected] (Bin Chen) writes:
>>
>> [...]
>>
>> > Are there any other good X86 emulator that can be easily extended by
>> > user?
>>
>> VMware isn't an emulator, it's a virtualizer.
>
> Why do you say it is not an emulator? Isn't a virtualizer just an
> emulator taking advantage of large similarities between the host
> architecture and the emulated architecture?
It's not an emulator in the sense that Bochs most definitely is.
That's all I meant. I think that you're right that the difference is
probably one of degree rather than kind---both bochs and VMware have
to emulate (or trap, anyway) some instructions.
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Message 15 in thread
寄件者：Bin Chen ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 18:23:31 PST
Bruce Stephens wrote in message news:<[email protected]>...
> [email protected] (Bin Chen) writes:
>
> [...]
>
> > Are there any other good X86 emulator that can be easily extended by
> > user?
>
> VMware isn't an emulator, it's a virtualizer. Bochs is an emulator
> (and so will run on non-ix86 hardware, which VMware won't). plex86
> is a project to develop
> an open source virtualizer, but I don't know that it works yet.
>
> valgrind also includes an x86 emulator; a performance comparison
> between valgrind and bochs might be interesting.
So what is the difference between an emulator and a virtalizer?
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Message 16 in thread
寄件者：TCS ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 19:50:16 PST
In article <[email protected]>, Bin Chen wrote:
>Bruce Stephens wrote in message news:<[email protected]>...
>> [email protected] (Bin Chen) writes:
>>
>> [...]
>>
>> > Are there any other good X86 emulator that can be easily extended by
>> > user?
>>
>> VMware isn't an emulator, it's a virtualizer. Bochs is an emulator
>> (and so will run on non-ix86 hardware, which VMware won't). plex86
>> is a project to develop
>> an open source virtualizer, but I don't know that it works yet.
>>
>> valgrind also includes an x86 emulator; a performance comparison
>> between valgrind and bochs might be interesting.
>So what is the difference between an emulator and a virtalizer?
One is a real word, the other is made up.
Same thing otherwise.
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Message 17 in thread
寄件者：David Konerding ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 22:01:35 PST
In article <[email protected]>, Bin Chen wrote:
> Bruce Stephens wrote in message news:<[email protected]>...
>> [email protected] (Bin Chen) writes:
>>
>> [...]
>>
>> > Are there any other good X86 emulator that can be easily extended by
>> > user?
>>
>> VMware isn't an emulator, it's a virtualizer. Bochs is an emulator
>> (and so will run on non-ix86 hardware, which VMware won't). plex86
>> is a project to develop
>> an open source virtualizer, but I don't know that it works yet.
>>
>> valgrind also includes an x86 emulator; a performance comparison
>> between valgrind and bochs might be interesting.
>
> So what is the difference between an emulator and a virtalizer?
An emulator completely emulates the host architecture. You
can emulate an Alpha chip on an x86 chip: the operating system or
application instructions are converted from the native format to
the host format and executed in the host instruction set.
In a virtualizer, the guest OS or application is run directly on
the host CPU, with little or no translation. Typically, all I/O
operations are trapped by the virtualization software and converted
to host OS operations.
VMware is a virtualizer; if you run a CPU-bound code,
nearly all the instructions run directly on the CPU.
I think bochs is a host emulator, and every instruction
is apparently converted by the hosting application, into a collection
of application instructions. CPU-bound operations run at native
speed in VMware, and I/O ops run a good fraction of the native
speed.
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Message 18 in thread
寄件者：Tim Roberts ([email protected])
主旨：Re: About VMware's 'virtual disk' file format?
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新闻群组：comp.os.linux.development.system
日期：2002-11-23 22:47:22 PST
[email protected] (Bin Chen) wrote:
>Bruce Stephens wrote:
>> [email protected] (Bin Chen) writes:
>>
>> > Are there any other good X86 emulator that can be easily extended by
>> > user?
>>
>> VMware isn't an emulator, it's a virtualizer. Bochs is an emulator
>> (and so will run on non-ix86 hardware, which VMware won't). plex86
>> is a project to develop
>> an open source virtualizer, but I don't know that it works yet.
>>
>> valgrind also includes an x86 emulator; a performance comparison
>> between valgrind and bochs might be interesting.
>
>So what is the difference between an emulator and a virtalizer?
Bochs, which is an emulator, reads the individual bytes in a program and
interprets them as an x86 processor would. When it reads an "add"
instruction, it modifies a variable stored in a structure in memory.
In VMWare, on the other hand, the x86 instructions are actually being
executed by the native processor. Only when an interrupt or an I/O port or
a device register gets accessed does VMWare itself actually get involved in
the process.
The difference is large.
--
- Tim Roberts, [email protected]
Providenza & Boekelheide, Inc.
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[已被 sunwen 编辑过，在 2002-11-24 21:34]
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