I normally never use undo disks, but now I'm thinking I'll start. I
would like to know whether using them is a performance hit or a
performance boost.

I'm thinking that it could go either way. When reading, the VM has to
figure out whether the data it wants is on the VHD, or if there's an
updated version of the data on the temporary file of the undo disk.
Writing should be easier and quicker I would think, as it's only got to
write to the smaller and quicker undo disk.



Has anyone done tests to see if it's quicker running with or without
undo disks? (not counting the final update period at the end, I don't
care about that, I'm only interested in run-time performance).

d d wrote:

> I normally never use undo disks, but now I'm thinking I'll start. I
> would like to know whether using them is a performance hit or a
> performance boost.
>
> I'm thinking that it could go either way. When reading, the VM has to
> figure out whether the data it wants is on the VHD, or if there's an
> updated version of the data on the temporary file of the undo disk.
> Writing should be easier and quicker I would think, as it's only got to
> write to the smaller and quicker undo disk.
>
> Has anyone done tests to see if it's quicker running with or without
> undo disks? (not counting the final update period at the end, I don't
> care about that, I'm only interested in run-time performance).

I also wonder how they can work with saved machine states. When I choose
to close a VM that has undo disks enabled, can I still choose to save
state? and if I do that, I assume I won't get asked about the undo disk
commit because I haven't yet chosen to shutdown the VM. Can I continue
to do that session after session? I'm assuming so, but don't need to try
it right now so I figured I'd just ask first.

d d's previous post was like this :

>
> d d wrote:

> > I normally never use undo disks, but now I'm thinking I'll start. I
> > would like to know whether using them is a performance hit or a
> > performance boost.
> >
> > I'm thinking that it could go either way. When reading, the VM has to
> > figure out whether the data it wants is on the VHD, or if there's an
> > updated version of the data on the temporary file of the undo disk.
> > Writing should be easier and quicker I would think, as it's only got to
> > write to the smaller and quicker undo disk.
> >
> > Has anyone done tests to see if it's quicker running with or without
> > undo disks? (not counting the final update period at the end, I don't
> > care about that, I'm only interested in run-time performance).

>
> I also wonder how they can work with saved machine states. When I choose
> to close a VM that has undo disks enabled, can I still choose to save
> state? and if I do that, I assume I won't get asked about the undo disk
> commit because I haven't yet chosen to shutdown the VM. Can I continue
> to do that session after session? I'm assuming so, but don't need to try
> it right now so I figured I'd just ask first.

I suppose performace lose, using undo disk,
for the need to work with 2 files simultaneously,
and due probably more complex data.

As far as I remember, I was able to save state, using undo disk.
undo and state saving are independent features.

--
Poutnik
The best choice is such a choice,
that causes the least number of people
to complain it is NOT the best choice.

Poutnik wrote:

> d d's previous post was like this :

>> d d wrote:

>>> I normally never use undo disks, but now I'm thinking I'll start. I
>>> would like to know whether using them is a performance hit or a
>>> performance boost.
>>>
>>> I'm thinking that it could go either way. When reading, the VM has to
>>> figure out whether the data it wants is on the VHD, or if there's an
>>> updated version of the data on the temporary file of the undo disk.
>>> Writing should be easier and quicker I would think, as it's only got to
>>> write to the smaller and quicker undo disk.
>>>
>>> Has anyone done tests to see if it's quicker running with or without
>>> undo disks? (not counting the final update period at the end, I don't
>>> care about that, I'm only interested in run-time performance).

>> I also wonder how they can work with saved machine states. When I choose
>> to close a VM that has undo disks enabled, can I still choose to save
>> state? and if I do that, I assume I won't get asked about the undo disk
>> commit because I haven't yet chosen to shutdown the VM. Can I continue
>> to do that session after session? I'm assuming so, but don't need to try
>> it right now so I figured I'd just ask first.

>
> I suppose performace lose, using undo disk,
> for the need to work with 2 files simultaneously,
> and due probably more complex data.
>
> As far as I remember, I was able to save state, using undo disk.
> undo and state saving are independent features.

I tried having undo disk on and closing the VM and wanted to just save
state (and leave the undo disk active). It didn't seem to offer me that
option. It's as if I have to save the undo disk changes regardless of
the fact that I'm not trying to shut down and only want to save state.

I guess I'll have to forget undo disks and just keep making a backup of
my VHD files more often than I'd like to.

d d's previous post was like this :

>

> I tried having undo disk on and closing the VM and wanted to just save
> state (and leave the undo disk active). It didn't seem to offer me that
> option. It's as if I have to save the undo disk changes regardless of
> the fact that I'm not trying to shut down and only want to save state.
>
> I guess I'll have to forget undo disks and just keep making a backup of
> my VHD files more often than I'd like to.

I turned on for the test Undo option again, running W2k under VPC2007.

When closing, it offers roll out menu:

Save state and save changes ( I understand as keep undo content )
Shut down and save changes
Turn off and save changes
Turn off and delete changes

furthermore, there is check out/in option:

Commit changes to virtual harddisk. ( Undo -> VHD )

Note that in VM settings, there is option
to show only some of shutdown options.

--
Poutnik
The best choice is such a choice,
that causes the least number of people
to complain it is NOT the best choice.

Poutnik wrote:

> d d's previous post was like this :
>

>> I tried having undo disk on and closing the VM and wanted to just save
>> state (and leave the undo disk active). It didn't seem to offer me that
>> option. It's as if I have to save the undo disk changes regardless of
>> the fact that I'm not trying to shut down and only want to save state.
>>
>> I guess I'll have to forget undo disks and just keep making a backup of
>> my VHD files more often than I'd like to.

>
> I turned on for the test Undo option again, running W2k under VPC2007.
>
> When closing, it offers roll out menu:
>
> Save state and save changes ( I understand as keep undo content )
> Shut down and save changes
> Turn off and save changes
> Turn off and delete changes
>
> furthermore, there is check out/in option:
>
> Commit changes to virtual harddisk. ( Undo -> VHD )
>
> Note that in VM settings, there is option
> to show only some of shutdown options.

Ok, I got it now. Thanks. It can do what I want (close the VM saving
state AND keeping the undo disk active). I just did some tests and it is
just what I need :-)