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disk size when converting dynamic hard disk to fixed disk

Source: microsoft.public.virtualserver
Sent: 04/04/2009
From: chris r
Message:

When I want to convert a dynamically expanding virtual disk to a fixed size
hd, I do not have the option to specify the fixed size. It seems that VS 2005
R2 will convert to the maximum size set when the dynamic disk was first
created. In my case, the default of 127GB was set as the maximum, which is
much larger than the 30GB fixed I want. Is there a way to do this with a
dynamic disk that has data already?

For reference, I perform Virtual Disks > Inspect > (select disk) > Inspect >
Convert virtual hard disk > (select location and name of new fixed disk). I
get the error "The virtual hard disk operation could not be performed. The
host volume does not have enough space to complete this disk operation."
which makes me think it wants to create a 127GB disk since I have just over
100GB host disk space left and it doesn't ask me for a size for the new disk.

- Chris

Post Reply | This is Spam! | Mark as Spam

Related Messages

Re: disk size when converting dynamic hard disk to fixed disk

Sent: 04/04/2009
From: chris r
Message:

Thanks for your response Bo. I understand the details of dynamic and fixed
disks and you confirmed that VS wants to convert the dynamic disk to the
maximum size set when it was created. I am surprised and think it is an
unreasonable limitation if it is indeed true that the fixed size cannot be
changed from the one selected at the very beginning. As Paul said and as MS
states, a fixed disk has performance advantages. And you a right that a
dynamic disk also has advantages.

Can anyone confirm that VS has this limitation on fixed disk size when
converting a dynamically expanding hd?

- chris

"Bo Berglund" wrote:

Show quoted text

> On Sat, 4 Apr 2009 13:52:01 -0700, chris r
> <(email address - cut out)> wrote:
>
> >When I want to convert a dynamically expanding virtual disk to a fixed size
> >hd, I do not have the option to specify the fixed size. It seems that VS 2005
> >R2 will convert to the maximum size set when the dynamic disk was first
> >created. In my case, the default of 127GB was set as the maximum, which is
> >much larger than the 30GB fixed I want. Is there a way to do this with a
> >dynamic disk that has data already?
> >
> >For reference, I perform Virtual Disks > Inspect > (select disk) > Inspect >
> >Convert virtual hard disk > (select location and name of new fixed disk). I
> >get the error "The virtual hard disk operation could not be performed. The
> >host volume does not have enough space to complete this disk operation."
> >which makes me think it wants to create a 127GB disk since I have just over
> >100GB host disk space left and it doesn't ask me for a size for the new disk.
> >
>
> When you create a virtual hard disk at the start you are given the
> option to set its size. In thsi case you set it to 128 Gb.
> The difference between the next selection (dynamically expanding
> versus fixed) is that in the latter case ALL of the set size is
> allocated at once on the host system whereas in the dynamic case it
> will be allocated gradually as the virtual disk fills up with data.
>
> So you are dealing with a FIXED disk size residing on the host on a
> file thta is eiter this fixed size to begin with or is dynamically
> expanding towards it.
>
> When you convert a dynamic disk to a fixed disk VS will try to
> allocate the disk size that is not yet allocated, in this case brining
> the total up to 128 Gb. If you don't have that much free space on tyhe
> host then it cannot be done.
>
> Your only option now is to create a new empty virtual disk with the
> proper size and then use an omaging tool (Ghost or Acronis) to clone
> your big disk onto the smaller drive. But it makes small sense to
> me...
>
> Might I ask for the reason you want to do this? Clearly a dynamically
> expanding VHD is much more convenient than a fixed size one....
>
> --
>
> Bo Berglund (Sweden)
>

Re: disk size when converting dynamic hard disk to fixed disk

Sent: 04/04/2009
From: Dave Warren <(email address - cut out)>
Message:

In message <(email address - cut out)> chris r
<(email address - cut out)> was claimed to have wrote:

It's not a limitation specifically as much as a bit of confusion about
how VHDs work.

Think of a VHD like a physical hard drive, you can request a drive of
any size you want from the manufacturer, but that drive's size can't be
changed once you have it.

If you want a smaller or larger hard drive, you go get one of the
appropriate size and move your OS/data just the same in a virtual
environment as you would in a real one.

The only difference between dynamic and fixed size disk formats is the
storage method used on the host, but changing between formats isn't
something the guest is aware of.

Show quoted text

>Thanks for your response Bo. I understand the details of dynamic and fixed
>disks and you confirmed that VS wants to convert the dynamic disk to the
>maximum size set when it was created. I am surprised and think it is an
>unreasonable limitation if it is indeed true that the fixed size cannot be
>changed from the one selected at the very beginning. As Paul said and as MS
>states, a fixed disk has performance advantages. And you a right that a
>dynamic disk also has advantages.
>
>Can anyone confirm that VS has this limitation on fixed disk size when
>converting a dynamically expanding hd?

Re: disk size when converting dynamic hard disk to fixed disk

Sent: 04/04/2009
From: Paul Adare <(email address - cut out)>
Message:

On Sun, 05 Apr 2009 00:13:14 +0200, Bo Berglund wrote:

Performance is better with fixed disks and all of the guidance from
Microsoft suggests using fixed rather than dynamic in production.

--
Paul Adare
MVP - Identity Lifecycle Manager
http://www.identit.ca

Show quoted text

> Might I ask for the reason you want to do this? Clearly a dynamically
> expanding VHD is much more convenient than a fixed size one....

Re: disk size when converting dynamic hard disk to fixed disk

Sent: 04/05/2009
From: Bo Berglund <(email address - cut out)>
Message:

On Sat, 4 Apr 2009 13:52:01 -0700, chris r
<(email address - cut out)> wrote:

When you create a virtual hard disk at the start you are given the
option to set its size. In thsi case you set it to 128 Gb.
The difference between the next selection (dynamically expanding
versus fixed) is that in the latter case ALL of the set size is
allocated at once on the host system whereas in the dynamic case it
will be allocated gradually as the virtual disk fills up with data.

So you are dealing with a FIXED disk size residing on the host on a
file thta is eiter this fixed size to begin with or is dynamically
expanding towards it.

When you convert a dynamic disk to a fixed disk VS will try to
allocate the disk size that is not yet allocated, in this case brining
the total up to 128 Gb. If you don't have that much free space on tyhe
host then it cannot be done.

Your only option now is to create a new empty virtual disk with the
proper size and then use an omaging tool (Ghost or Acronis) to clone
your big disk onto the smaller drive. But it makes small sense to
me...

Might I ask for the reason you want to do this? Clearly a dynamically
expanding VHD is much more convenient than a fixed size one....

--

Bo Berglund (Sweden)

Show quoted text

>When I want to convert a dynamically expanding virtual disk to a fixed size
>hd, I do not have the option to specify the fixed size. It seems that VS 2005
>R2 will convert to the maximum size set when the dynamic disk was first
>created. In my case, the default of 127GB was set as the maximum, which is
>much larger than the 30GB fixed I want. Is there a way to do this with a
>dynamic disk that has data already?
>
>For reference, I perform Virtual Disks > Inspect > (select disk) > Inspect >
>Convert virtual hard disk > (select location and name of new fixed disk). I
>get the error "The virtual hard disk operation could not be performed. The
>host volume does not have enough space to complete this disk operation."
>which makes me think it wants to create a 127GB disk since I have just over
>100GB host disk space left and it doesn't ask me for a size for the new disk.
>

Re: disk size when converting dynamic hard disk to fixed disk

Sent: 04/05/2009
From: Bo Berglund <(email address - cut out)>
Message:

On Sat, 4 Apr 2009 15:44:03 -0700, chris r >
<(email address - cut out)> wrote:

What if you had bought a disk drive of a certain size for your real
computer and used it for a while and now you want to have a different
size? Would you require the disk maker to supply a tool to change the
size of the drive?? Of course not! You know thta it can't be done!
So why do you request this from a virtual drive that behaves exactly
like a physical drive to the installed operating system on the guest?

For starters think about the way the installed operating system in the
guest works:
It does not know that it is running on anything but a real hard drive
of 128 Gb in size, so even though you have only 30 Gb of data stored
on it the opertating system may have placed that data in sectors all
over the disk including at the beginning and at the end of the disk.
This location of chunks of data will be recorded in various other
places on the disk, which is operating system and disk format
specific. For FAT it is the FAT table and for NTFS there is the MFT
data etc.

Now if an *external* program on the host should change the storage
format of the VHD drive such that it also changes the size of the disk
then what should it do about data that are stored at the end of the
disk way beyond the new smaller disk limit you want to apply?
Should it discard that data or should it move it? If move then *how*
should it do it? It is not just a case of somehow fitting it into free
space on the smaller disk, it needs to do it in the way the installed
operating system could understand too....

The only way this could be accomplished is if ALL data on the disk
resides in the low part of the disk area such that it would be
possible to *inside* the guest operating system reduce the disk
partition size. But it means that you have to apply a defragging
operation first that moves all data to the start of the disk as a
contiguous chunk. Problem is that most defraggers do not work that
way, they make files contiguous but leave holes between files.

So, still the only possible way is to do the operation like this:

1) Create a new empty virtual disk of the needed size.
2) Attach this to the guest
3) Start the guest and install Acronis or another imaging software
4) Use it to clone the system drive onto the new empty drive.
5) Shut down the guest
6) Reassign the dives such that the new drive is now the only one
7) Start up again.

This is the safe and working way and it works because it is done as an
operation *inside* the running guest using software that is operating
system specific and understands the way the data are layed out on the
disk.
Notice that this is *exactly* like you would have done it on a
physical computer when you move from one drive to another.

Might be, but I have not noted especially big impacts. Is there an
actual test benchmarking these performance differences. Dynamic
expanding disks have a great advantage on the host in thta they only
grow as data are added. As seen from the *host* of course!

--

Bo Berglund (Sweden)

Show quoted text

>"Bo Berglund" wrote:
>
>> On Sat, 4 Apr 2009 13:52:01 -0700, chris r
>> <(email address - cut out)> wrote:
>>
>> >When I want to convert a dynamically expanding virtual disk to a fixed size
>> >hd, I do not have the option to specify the fixed size. It seems that VS 2005
>> >R2 will convert to the maximum size set when the dynamic disk was first
>> >created. In my case, the default of 127GB was set as the maximum, which is
>> >much larger than the 30GB fixed I want. Is there a way to do this with a
>> >dynamic disk that has data already?
>> >
>> >For reference, I perform Virtual Disks > Inspect > (select disk) > Inspect >
>> >Convert virtual hard disk > (select location and name of new fixed disk). I
>> >get the error "The virtual hard disk operation could not be performed. The
>> >host volume does not have enough space to complete this disk operation."
>> >which makes me think it wants to create a 127GB disk since I have just over
>> >100GB host disk space left and it doesn't ask me for a size for the new disk.
>> >
>>
>> When you create a virtual hard disk at the start you are given the
>> option to set its size. In thsi case you set it to 128 Gb.
>> The difference between the next selection (dynamically expanding
>> versus fixed) is that in the latter case ALL of the set size is
>> allocated at once on the host system whereas in the dynamic case it
>> will be allocated gradually as the virtual disk fills up with data.
>>
>> So you are dealing with a FIXED disk size residing on the host on a
>> file thta is eiter this fixed size to begin with or is dynamically
>> expanding towards it.
>>
>> When you convert a dynamic disk to a fixed disk VS will try to
>> allocate the disk size that is not yet allocated, in this case brining
>> the total up to 128 Gb. If you don't have that much free space on tyhe
>> host then it cannot be done.
>>
>> Your only option now is to create a new empty virtual disk with the
>> proper size and then use an omaging tool (Ghost or Acronis) to clone
>> your big disk onto the smaller drive. But it makes small sense to
>> me...
>>
>> Might I ask for the reason you want to do this? Clearly a dynamically
>> expanding VHD is much more convenient than a fixed size one....
>>
>Thanks for your response Bo. I understand the details of dynamic and fixed
>disks and you confirmed that VS wants to convert the dynamic disk to the
>maximum size set when it was created. I am surprised and think it is an
>unreasonable limitation if it is indeed true that the fixed size cannot be
>changed from the one selected at the very beginning.
>As Paul said and as MS
>states, a fixed disk has performance advantages. And you a right that a
>dynamic disk also has advantages.
>Can anyone confirm that VS has this limitation on fixed disk size when
>converting a dynamically expanding hd?
>
>- chris
>

Re: disk size when converting dynamic hard disk to fixed disk

Sent: 04/05/2009
From: chris r
Message:

Thanks Dave and Bo -

I now understand that the guest OS may have placed data at the beginning and
end of the disk even though the real size of the VHD may be very small
compared, and making a fixed size disk may need to be as large as the max
size, from the perspective of the guest OS.

If there is no real data to support performance issues with dynamic disks,
that is good to know.

The suggestion to use imaging software is welcomed, thanks!

- chris

"Bo Berglund" wrote:

Show quoted text

> On Sat, 4 Apr 2009 15:44:03 -0700, chris r >
> >"Bo Berglund" wrote:
> >
> >> On Sat, 4 Apr 2009 13:52:01 -0700, chris r
> >> <(email address - cut out)> wrote:
> >>
> >> >When I want to convert a dynamically expanding virtual disk to a fixed size
> >> >hd, I do not have the option to specify the fixed size. It seems that VS 2005
> >> >R2 will convert to the maximum size set when the dynamic disk was first
> >> >created. In my case, the default of 127GB was set as the maximum, which is
> >> >much larger than the 30GB fixed I want. Is there a way to do this with a
> >> >dynamic disk that has data already?
> >> >
> >> >For reference, I perform Virtual Disks > Inspect > (select disk) > Inspect >
> >> >Convert virtual hard disk > (select location and name of new fixed disk). I
> >> >get the error "The virtual hard disk operation could not be performed. The
> >> >host volume does not have enough space to complete this disk operation."
> >> >which makes me think it wants to create a 127GB disk since I have just over
> >> >100GB host disk space left and it doesn't ask me for a size for the new disk.
> >> >
> >>
> >> When you create a virtual hard disk at the start you are given the
> >> option to set its size. In thsi case you set it to 128 Gb.
> >> The difference between the next selection (dynamically expanding
> >> versus fixed) is that in the latter case ALL of the set size is
> >> allocated at once on the host system whereas in the dynamic case it
> >> will be allocated gradually as the virtual disk fills up with data.
> >>
> >> So you are dealing with a FIXED disk size residing on the host on a
> >> file thta is eiter this fixed size to begin with or is dynamically
> >> expanding towards it.
> >>
> >> When you convert a dynamic disk to a fixed disk VS will try to
> >> allocate the disk size that is not yet allocated, in this case brining
> >> the total up to 128 Gb. If you don't have that much free space on tyhe
> >> host then it cannot be done.
> >>
> >> Your only option now is to create a new empty virtual disk with the
> >> proper size and then use an omaging tool (Ghost or Acronis) to clone
> >> your big disk onto the smaller drive. But it makes small sense to
> >> me...
> >>
> >> Might I ask for the reason you want to do this? Clearly a dynamically
> >> expanding VHD is much more convenient than a fixed size one....
> >>
> <(email address - cut out)> wrote:
>
> >Thanks for your response Bo. I understand the details of dynamic and fixed
> >disks and you confirmed that VS wants to convert the dynamic disk to the
> >maximum size set when it was created. I am surprised and think it is an
> >unreasonable limitation if it is indeed true that the fixed size cannot be
> >changed from the one selected at the very beginning.
>
> What if you had bought a disk drive of a certain size for your real
> computer and used it for a while and now you want to have a different
> size? Would you require the disk maker to supply a tool to change the
> size of the drive?? Of course not! You know thta it can't be done!
> So why do you request this from a virtual drive that behaves exactly
> like a physical drive to the installed operating system on the guest?
>
> For starters think about the way the installed operating system in the
> guest works:
> It does not know that it is running on anything but a real hard drive
> of 128 Gb in size, so even though you have only 30 Gb of data stored
> on it the opertating system may have placed that data in sectors all
> over the disk including at the beginning and at the end of the disk.
> This location of chunks of data will be recorded in various other
> places on the disk, which is operating system and disk format
> specific. For FAT it is the FAT table and for NTFS there is the MFT
> data etc.
>
> Now if an *external* program on the host should change the storage
> format of the VHD drive such that it also changes the size of the disk
> then what should it do about data that are stored at the end of the
> disk way beyond the new smaller disk limit you want to apply?
> Should it discard that data or should it move it? If move then *how*
> should it do it? It is not just a case of somehow fitting it into free
> space on the smaller disk, it needs to do it in the way the installed
> operating system could understand too....
>
> The only way this could be accomplished is if ALL data on the disk
> resides in the low part of the disk area such that it would be
> possible to *inside* the guest operating system reduce the disk
> partition size. But it means that you have to apply a defragging
> operation first that moves all data to the start of the disk as a
> contiguous chunk. Problem is that most defraggers do not work that
> way, they make files contiguous but leave holes between files.
>
> So, still the only possible way is to do the operation like this:
>
> 1) Create a new empty virtual disk of the needed size.
> 2) Attach this to the guest
> 3) Start the guest and install Acronis or another imaging software
> 4) Use it to clone the system drive onto the new empty drive.
> 5) Shut down the guest
> 6) Reassign the dives such that the new drive is now the only one
> 7) Start up again.
>
> This is the safe and working way and it works because it is done as an
> operation *inside* the running guest using software that is operating
> system specific and understands the way the data are layed out on the
> disk.
> Notice that this is *exactly* like you would have done it on a
> physical computer when you move from one drive to another.
>
> >As Paul said and as MS
> >states, a fixed disk has performance advantages. And you a right that a
> >dynamic disk also has advantages.
>
> Might be, but I have not noted especially big impacts. Is there an
> actual test benchmarking these performance differences. Dynamic
> expanding disks have a great advantage on the host in thta they only
> grow as data are added. As seen from the *host* of course!
>
> >Can anyone confirm that VS has this limitation on fixed disk size when
> >converting a dynamically expanding hd?
> >
> >- chris
> >
>
> --
>
> Bo Berglund (Sweden)
>

Re: disk size when converting dynamic hard disk to fixed disk

Sent: 04/10/2009
From: Artunc
Message:

Check this link out. Let me know if anyone find an easier and faster way
than this.

http://blogs.technet.com/tonyso/archive/2008/10/09/hyper-v-how-to-shrink-a-vhd-file.aspx

"Bo Berglund" wrote:

Show quoted text

Post Reply | This is Spam! | Mark as Spam

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