Enquiring Mind said:
Anna,
Thank you for explaining in further detail how Casper accomplishes the
task of creating disk clones, how it achieves relatively quick
performance, and the rationale for using it.
Without any hands-on experience of any disk imaging or disk cloning
program, other than tools that ship with the operating system, I can see
that both approaches have advantages and disadvantages. This my assessment
based on the information provided in this thread:
A. Disc imaging approach
1. Since the disk image is a single file, we can back up multiple disks to
a single disk without having to partition the disk. The disk will simply
contain one image file for each source disk.
2, The size of the disk image file generated is approximately equal to the
volume of data on the source disk. Thus if the source disk has a capacity
of 80 GB but only contains 3 GB of data, then the image file will be in
the region of 3GB in size. On the other hand, a disk clone must be created
to accommodate the full size of the source disk, in this case 80 GB.
3. The disk image file can be encrypted and/or compressed.
4. The disk image file is a file, not a bootable disk, so in the event of
the death of the source disk more work needs to be done to recover the
data from the image file to a bootable disk.
5. Multiple image files for a succession of back-ups can be accommodated
in a single disk/partition (of sufficient size).
B. Disk cloning approach
1. We need a separate disk or partition for each source disk or partition
that we wish to backup. Not suitable for maintaining a succession of
backups.
2. The disk clone, if on an external hard drive, may make private files
public, but cannot be easily encrypted.
3. The disk clone makes system restoration a breeze if on an internal HD.
4. Backup to a disk clone is very simple, because there are few choices to
be made.
I shall need to weigh up the pros and cons as they have a number of
implications! But the disk cloning approach does sound like an attractive
option!
Regards,
EM
EM:
By & large I think you've covered the basic differences between disk-cloning
& disk-imaging as they apply to creating a comprehensive backup system for
one's PC.
Just a few comments...
With respect to the disk-imaging approach (referring to your numbered items
above)...
1. Keep in mind that while the *original* disk-image (Acronis refers to it
as an "archive") created by the user is a single file, presumably the user
will be subsequently creating *incremental* files ("archives") necessary to
maintain up-to-date backups of one's system. Both the original file
(archive) and subsequent incremental files will ordinarily be retained until
either they're used for recovery purposes or the user decides the sheer
number of them is too unwieldy to continue and simply "starts over" by
creating a new "original" disk-image backup, deleting the existing
files/archives in the process.
While there's no need to create multiple partitions on the "destination"
drive to serve as the recipient of these disk-images, folders would
ordinarily be created to house the images from different "source" HDDs.
In any event, please do not attach too much importance to the issue of
creating partitions on the destination HDD either in terms of difficulty or
amount of time needed to do so. This is a very simple operation that can be
easily achieved through XP's Disk Management snap-in or using the Casper 5
program during its disk-cloning operation.
2. With respect to the disk-image, there will (usually) be a certain amount
of compression provided by the program so that the resultant file/archive
will be somewhat smaller than the actual size of the contents that are
imaged. In the case of the Acronis program we have generally found that this
reduction via compression is somewhat in the order of 20% - 25%. So, taking
your example, of 3 GB of contents being "imaged", the resultant file/image
would be about 2.5 GB or so.
But you've misunderstood this situation with respect to the disk-cloning
process. (Again, my comments refer specifically to the Casper 5 program)...
Again, using your example of an 80 GB HDD (or partition) that contains 3 GB
of data, as I previously explained, the user could easily create a partition
on the destination drive *equal* to the size of the data being cloned - in
this case, 3 GB. Or, he or she could create a larger size to anticipate
future increases in the size of data subsequently cloned. The choice of the
size of the partition rests with the user, the *only* limitation being that
the partition must be of sufficient size to contain the cloned contents.
And, of course, there is no compression of data using the disk-cloning
process. A clone is a clone is a clone.
It is true that in the usual scenario - where a user has a single day-to-day
working HDD (which probably represents the overwhelming number of cases) -
that user will employ the "destination" drive (internal or external) as the
dedicated recipient of the cloned contents of their source HDD and simply
create disk-to-disk clones and not be concerned in any way with partition
manipulation. In your situation where you're working with two different PCs
and apparently desire a single USBEHD to serve as the recipient of the data
from each of those two PCs, obviously the creation/manipulation of
partitions is important.
In many cases we find that where a user is working with both a
laptop/notebook and a desktop machine they simply use two separate drives to
serve as recipients of the clones from each machine. Given the dramatic
decreases in costs for these devices over the past few years it's not a
terribly expensive proposition for many users to go that route.
3. See above re the compression issue.
4. Yes, you have it right. There's a "recovery" process that is necessary,
but it's not particularly onerous or too terribly time-demanding. In any
event, what is important is that the process be *effective*, not the amount
of time it takes to return the system to a bootable, functional state. As I
have tried to point out in my previous posts, it is the routine *backup*
operation that's important from an expenditure of (user) time point-of-view.
Presumably, in the vast bulk of cases, the user will be performing scores,
if not hundreds, of backup operations before a recovery of the system will
become necessary. It's this extroardinary speed of the backup operation
(cloning) that makes the Casper 5 program so superior in my view. But as I
have emphasized the program must be used with reasonable frequency to
achieve this advantage.
5. Yes, I'm assuming you're referring to incremental disk-image files
(archives) here.
With respect to your observations re the disk-cloning process...
Yes, as I've previously indicated, should a user be primarily interested in
maintaining "generational" copies of his/her system at various
points-in-time, a disk-imaging program lends itself better to that goal.
While relatively few home PC users are interested in that objective, in that
they are exclusively interested in maintaining an up-to-date backup of their
system(s), many commercial entities require that capability for obvious
reasons.
While a disk-cloning program could be used to some extent for that purpose,
it would depend upon the volume of data to be cloned together with the size
(disk-space) of the destination drive(s). For example, we know of a number
of Casper 5 users who are interested in retaining 2, 3, or 4 previous clones
of their systems and in many cases this can be easily accommodated given the
enormous capacity of today's HDDs - both internal & external.
May I again suggest, as I've done throughout this entire thread, the only
*real* way to determine which program best meets your needs is to experiment
with them. In the final analysis, only a "hands-on" approach will determine
what's best for you. Fortunately, many of these programs have demo or trial
versions available so you can gain at least some understanding as to whether
this one or that one will best serve you. And, as you have discovered, there
are a number of freely available programs you can test out as well.
What I'm trying to impress upon you (and others) is simply this...
Don't rely on theoretical explanations (from me or anyone else) of what this
program or that program or this approach or that approach can do or not do
for you. Work with these different programs as best you can so that you -
and only you - will determine the appropriate approach/program needed in
your unique situation.
Anna
