Difference between a Disk Image and a Clone

[Harvey Gratt]

Can someone please supply a precise definition of each and what the
differences are?

Thanks,
Harvey

 

[Rod Speed]

Can someone please supply a precise definition of each

A disk image is a file or set of files that contain all the
data from the disk its an image of. It can also be an image
of just a partition, rather than the entire physical disk.

An image needs to be restored to a physical drive before it can
be used, tho most imaging programs do provide some way to
browse images so that individual files can be extracted etc.

A clone is an exact copy of a disk, to another physical disk.

A clone can also be a clone of a partition rather than a physical disk.

and what the differences are?

The most important difference with an image is that
it cant be used as it is for normal operations and
cant be booted etc. It needs to be restored first.

A cloned disk can do anything the original disk can do.

 

[Harvey Gratt]

Thanks.

Are there size differences between the two formats (image vs disk, i.e.,
is the image a compressed file, is the clone a compressed file or does
it retain a file structure, does the clone need to have the same file
structure, NTFS, FAT32 as the original disk)? What would be the
advantage of one over the other? Can individual files be extracted from
a clone?

Thanks,
Harvey

 

[Rod Speed]

Thanks.

Are there size differences between the two formats
(image vs disk, i.e., is the image a compressed file,

Yes, tho most imaging programs allow you to specify if there
is compression or no compression at all for a higher speed.
And the image file normally doesnt include the free space either.

is the clone a compressed file

Nope, its an exact copy of the original.

or does it retain a file structure, does the clone need to have
the same file structure, NTFS, FAT32 as the original disk)?

Yep. Tho some programs can convert as well as clone.

What would be the advantage of one over the other?

Image files are normally much smaller, particularly with
maximum compression. That allows you to have more than
one image on the drive thats used to store the image files.

Can individual files be extracted from a clone?

Yes, its just a normal disk or partition and any normal file
ops can be done on the clone, using the standard file ops
too. With an image file you can READ files from the image
but normally need to use the imaging program's browser
to do that, and its not as easy to add files to the image,
tho some imaging programs do allow that.

 

[Harvey Gratt]

Rod,

Thanks again. I appreciate you taking the time to answer. One more
question concerning the clone file structure - my original question was
not clear:

If my external HDD is formatted as FAT32, can I clone a disk which has
its OS as NTFS or do I need to make an NTFS partition on the external
HDD. Or, would the cloning software convert the NTFS to FAT32 (if so, I
guess I lose the NTFSF formmating for later use).

Thanks,
Harvey

 

[CJT]

A disk image is a file or set of files that contain all the
data from the disk its an image of. It can also be an image
of just a partition, rather than the entire physical disk.

An image needs to be restored to a physical drive before it can
be used, tho most imaging programs do provide some way to
browse images so that individual files can be extracted etc.

A clone is an exact copy of a disk, to another physical disk.

In that case, what Ghost calls a clone is not really a clone,
since it reorders clusters and can act between disks of different
sizes.

Something like dd would be the only software that creates clones
under that definition.

 

[Rod Speed]

Thanks again. I appreciate you taking the time to
answer. One more question concerning the clone
file structure - my original question was not clear:

If my external HDD is formatted as FAT32, can
I clone a disk which has its OS as NTFS or do I
need to make an NTFS partition on the external HDD.

The original format of the external HDD is completely irrelevant.
The program that does the cloning basically replaces what is
on the external HDD with the clone of the internal disk, losing
the original format of the external HDD in the process.

 

[Rod Speed]

In that case, what Ghost calls a clone is not really a clone, since
it reorders clusters and can act between disks of different sizes.

Sure, but it is a clone in the sense that
its operationally a complete copy.

And you can actually specify a sector by sector true
clone too with one of the command line switches.

And decent clone software allows the clone to be on a physically
larger drive than the original for operational convenience.

Something like dd would be the only software
that creates clones under that definition.

Ghost can do that too if you want to do that sort of true clone.

And true cloning should really have some mechanism
for dealing with bad sectors on the original too, because
thats one situation where true cloning is sometimes used,
when the original has either got royally screwed and you
want to try various approaches to recovery on the copy,
or the original is dying and you want to maximise the
chances of getting all you can off the original.

 

[Timothy Daniels]

"Harvey Gratt" asked:

If my external HDD is formatted as FAT32, can I clone a disk which has
its OS as NTFS or do I need to make an NTFS partition on the external
HDD. Or, would the cloning software convert the NTFS to FAT32 (if so,
I guess I lose the NTFSF formmating for later use).

Cloning implies a byte-for-byte copy of a drive (logical or physical),
and that implies a copy of the formatting as well. So a clone has the
same formatting as the original.

*TimDaniels*

 

[Timothy Daniels]

In that case, what Ghost calls a clone is not really a clone,
since it reorders clusters and can act between disks of different
sizes.

He meant "drive" - either logical or physical - instead of "disk"

*TimDaniels*

 

[Rod Speed]

Harvey Gratt wrote.

Cloning implies a byte-for-byte copy of a drive (logical or physical),

Nope. Its also a term used to cover a clone
that produces an operationally identical drive.

and that implies a copy of the formatting as well.
So a clone has the same formatting as the original.

Usually, but not always.

 

[Rod Speed]

CJT wrote

He meant "drive" - either logical or physical - instead of "disk"

Like hell I did.

 

[Timothy Daniels]

Nope. Its also a term used to cover a clone
that produces an operationally identical drive.

How can a byte-for-byte copy (implying a copy of the master
boot record as well) *not* be operationally identical, assuming
the BIOS boot sequence and the HD jumpers are set appropriately?

*TimDaniels*

 

[Timothy Daniels]

"Rod Speed" coughed:

Like hell I did.

You should have. Several logical drives can reside on a
physical disk and be bootable, and each can be independently
cloned to a partition on the same or another disk, resulting in
another bootable logical drive that is operationally identical to
the cloned drive.

*TimDaniels*

 

[Rod Speed]

Rod Speed wrote

How can a byte-for-byte copy (implying a copy of the
master boot record as well) *not* be operationally identical,

Never said anything about that. I JUST said that a byte
by byte copy isnt the only thing thats called cloning.

 

[Rod Speed]

Rod Speed wrote

You should have.

Nope, HE used that word and I normally use the same term
as the was used in the question to keep things simple.

No point in getting sidetracked on the
particular term with a question like that.

I did choose to spell out the difference
between a physical disk and a partition too.

Several logical drives can reside
on a physical disk and be bootable,

No news to me, boy. And not relevant to his question
about the difference between a clone and an image.

and each can be independently cloned
to a partition on the same or another disk,

No news to me boy. I said that.

resulting in another bootable logical drive that
is operationally identical to the cloned drive.

What I said using the word drive instead of disk.