Can I compress a partition and keep all the erased data?

[Mark M]

QUESTION

Is there a way to save a 160GB NTFS partition in a smaller space and
at the same time to retain ALL the data? That retained data would
include clusters of *erased* data and *erased* system files.

I believe that creating a typical image file of the 160Gb partition
would not include those erased data areas. But is there some other
way to do what I want?

--------

OBJECTIVE

My objective is to be able go back to this partition and to undelete
data as and when I might need to.

The 160GB partition contains XP Home and is on a PC which is only a
few months old. This means something like 100GB to 140GB of the
160GB is completely virgin space. It seems a pity not to reclaim
this 100GB+ space for use - but only if it's still possible to KEEP
the clusters which contain data but which are not "marked" to say
their data is normally available. (If you see what I mean!)

 

[Arno Wagner]

QUESTION

Is there a way to save a 160GB NTFS partition in a smaller space and
at the same time to retain ALL the data? That retained data would
include clusters of *erased* data and *erased* system files.

I believe that creating a typical image file of the 160Gb partition
would not include those erased data areas. But is there some other
way to do what I want?


My objective is to be able go back to this partition and to undelete
data as and when I might need to.

The 160GB partition contains XP Home and is on a PC which is only a
few months old. This means something like 100GB to 140GB of the
160GB is completely virgin space. It seems a pity not to reclaim
this 100GB+ space for use - but only if it's still possible to KEEP
the clusters which contain data but which are not "marked" to say
their data is normally available. (If you see what I mean!)

I think the problem is to determine which space contains data.
It might be infeasible in general. The only option I see is to do
a compressed image-backup (all sectors), where the empty sectors
are compressed very well (since they contain zeros). For that
you will need a target filesystem with enough space to store
the entire partition and a file-size limit also high enough.

Personally I don't know whether there are suotable sector imagers
under Windows. Under Linux you would do something like
cat /dev/sda1 | bzip2 -1 > image.bz2 and a verify afterwards,
e.g. by doing md5 sums of original and image. This might take
several days though.

Arno

 

[Rod Speed]

QUESTION

Is there a way to save a 160GB NTFS partition in a
smaller space and at the same time to retain ALL the data?
Yes.

That retained data would include clusters
of *erased* data and *erased* system files.
Yes.

I believe that creating a typical image file of the 160Gb
partition would not include those erased data areas.
Correct.

But is there some other way to do what I want?
Yes.



My objective is to be able go back to this partition
and to undelete data as and when I might need to.

The 160GB partition contains XP Home and is on a PC which
is only a few months old. This means something like 100GB to
140GB of the 160GB is completely virgin space. It seems a pity
not to reclaim this 100GB+ space for use - but only if it's still
possible to KEEP the clusters which contain data but which are not
"marked" to say their data is normally available. (If you see what I
mean!)

Yes.

What you need to do is to image the drive with an imager that can
put every sector into the image file. Most can do that optionally.

Then compress that image file with one of the archivers
like rar. That should keep just one copy of sectors that
have never been used by the OS and which are truly blank.

That way the sectors which have been used will
be kept, even if they are part of a deleted file.

If you find that the image file doesnt compress much,
that would be because the use of the drive hasnt been
as restricted to such a small subset of the drive as you
expect. In other words the OS did use many/most of the
sectors even tho most of the drive is free space. That
might happen if the drive has been quite active if the
OS has used virgin space instead of reusing used space.

It also wont work if something has been used which writes
random data to the drive to test it. Thats not that likely tho.

 

[Mark M]

I think the problem is to determine which space contains data.
It might be infeasible in general. The only option I see is to
do a compressed image-backup (all sectors), where the empty
sectors are compressed very well (since they contain zeros). For
that you will need a target filesystem with enough space to
store the entire partition and a file-size limit also high
enough.

Personally I don't know whether there are suotable sector
imagers under Windows. Under Linux you would do something like
cat /dev/sda1 | bzip2 -1 > image.bz2 and a verify afterwards,
e.g. by doing md5 sums of original and image. This might take
several days though.

Arno

Thanks for the feedback. I think the best way is to just take the
160 GB hard drive out, put it aside and replace it with a new one.