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what is 'disk imaging'?



 
 
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  #1  
Old February 1st 05, 12:18 AM
Vic
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Posts: n/a
Default what is 'disk imaging'?

Was going through posts in this group and saw a number of comments on 'disk imaging'. I've heard of 'imaging' from years back but
never understood what it is, or how someone can take an 'image' and restore all their data from an image to another drive. To me
imaging sounds like backing-up information, yet a disk image sounds very small in size compared to a backup.

Would is the difference between imaging and backing-up?
What is 'imaging'?

Thanks,
Vic


  #2  
Old February 1st 05, 12:39 AM
RJK
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http://www.google.com/search?hl=en&l...ging+explained

regards, Richard


"Vic" wrote in message
...
Was going through posts in this group and saw a number of comments on
'disk imaging'. I've heard of 'imaging' from years back but
never understood what it is, or how someone can take an 'image' and
restore all their data from an image to another drive. To me
imaging sounds like backing-up information, yet a disk image sounds very
small in size compared to a backup.

Would is the difference between imaging and backing-up?
What is 'imaging'?

Thanks,
Vic




  #3  
Old February 1st 05, 12:48 AM
David H. Lipman
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Posts: n/a
Default

Disk imaging is the process where the admin. runs software, outside of the Operating System
like booting DOS from a Floppy Disk, and creates an image of the entire hard disk. It is a
"snap shot" of the system at the point the system was imaged. The image could be a series
of disk files, stored on a Tape Drive, CD disks, DVD media, ZIP disks, etc. Using software
files can be extracted individually or enmasse from the image.

Using the software an image can be made and restored to a hard disk that isn't even
formatted. For example, lets say that an OS is running with a 20GB hard disk that has 1GB
free. An image can be made, a 60GB hard disk can be installed and the image restored to the
empty hard disk. Now you have the exact same system not with 1GB free hard disk space but a
system with 41GB free disk space.

Another example might be I have 10 identical model platforms. Lets say an IBM Thinkpad
A22m. I can install all the software on one of the notebooks. Completely configure all the
software. Depending on the OS, SysPrep the platform. Then an image can be created. Now
that image can be restored to the other nine platforms. Note this *only* works with
identical model platforms. When done, 10 systems will be setup exactly alike.

Two well know imaging packages are Norton/Symantec Ghost and Acronis True Image.

Imaging is more exact that backups. Backups are usually selected data but can be an entire
system. However, a backup will only copy data files on a hard disk. It will not create a
representation of the hard disk's partition table or file system. In the example above, if
an image is made of a Win2K platform using NTFS, the image can be restored to an bare hard
disk and the final object will be Win2K on NTFS. Another difference is that the backup
software usually runs under the OS. When this is done, programs and the Operating System
will hold File Handles open. This can be a hindrance to both backing those files up and
restoring them. This can be overcome by using a backup application that can be executed
outside the OS like off a floppy disk. However, to restore the files to a hard disk,. the
hard disk must be High Level Formatted.

HTH

--
Dave




"Vic" wrote in message
...
| Was going through posts in this group and saw a number of comments on 'disk imaging'. I've
heard of 'imaging' from years back but
| never understood what it is, or how someone can take an 'image' and restore all their data
from an image to another drive. To me
| imaging sounds like backing-up information, yet a disk image sounds very small in size
compared to a backup.
|
| Would is the difference between imaging and backing-up?
| What is 'imaging'?
|
| Thanks,
| Vic
|
|


  #4  
Old February 1st 05, 02:36 AM
Vic
external usenet poster
 
Posts: n/a
Default

David, what a great explanation. I appreciate the detail, it really help me understand the difference between backups and imaging.

One question still remains, is an image 'smaller' in size than the information it 'snap a shot' of (i.e. is an image COMPRESSED
information)?

TIA
Vic
___
"David H. Lipman" wrote in message ...
Disk imaging is the process where the admin. runs software, outside of the Operating System
like booting DOS from a Floppy Disk, and creates an image of the entire hard disk. It is a
"snap shot" of the system at the point the system was imaged. The image could be a series
of disk files, stored on a Tape Drive, CD disks, DVD media, ZIP disks, etc. Using software
files can be extracted individually or enmasse from the image.

Using the software an image can be made and restored to a hard disk that isn't even
formatted. For example, lets say that an OS is running with a 20GB hard disk that has 1GB
free. An image can be made, a 60GB hard disk can be installed and the image restored to the
empty hard disk. Now you have the exact same system not with 1GB free hard disk space but a
system with 41GB free disk space.

Another example might be I have 10 identical model platforms. Lets say an IBM Thinkpad
A22m. I can install all the software on one of the notebooks. Completely configure all the
software. Depending on the OS, SysPrep the platform. Then an image can be created. Now
that image can be restored to the other nine platforms. Note this *only* works with
identical model platforms. When done, 10 systems will be setup exactly alike.

Two well know imaging packages are Norton/Symantec Ghost and Acronis True Image.

Imaging is more exact that backups. Backups are usually selected data but can be an entire
system. However, a backup will only copy data files on a hard disk. It will not create a
representation of the hard disk's partition table or file system. In the example above, if
an image is made of a Win2K platform using NTFS, the image can be restored to an bare hard
disk and the final object will be Win2K on NTFS. Another difference is that the backup
software usually runs under the OS. When this is done, programs and the Operating System
will hold File Handles open. This can be a hindrance to both backing those files up and
restoring them. This can be overcome by using a backup application that can be executed
outside the OS like off a floppy disk. However, to restore the files to a hard disk,. the
hard disk must be High Level Formatted.

HTH

--
Dave




"Vic" wrote in message
...
| Was going through posts in this group and saw a number of comments on 'disk imaging'. I've
heard of 'imaging' from years back but
| never understood what it is, or how someone can take an 'image' and restore all their data
from an image to another drive. To me
| imaging sounds like backing-up information, yet a disk image sounds very small in size
compared to a backup.
|
| Would is the difference between imaging and backing-up?
| What is 'imaging'?
|
| Thanks,
| Vic
|
|




  #5  
Old February 1st 05, 02:54 AM
David H. Lipman
external usenet poster
 
Posts: n/a
Default

Yes Vic.

Actually both backups and images are compressed to save space. The assumption is a 2:1
compression ratio. This will vary based on the compressibility of the data. For example,
ZIP, CAB, JPEG and MPEG files are already compressed so they will not be compressed
appreciably in the image or backup media. But it is a good expectation that if you have
10GBs of data, you will need 5GB ~ 6GB worth of space. Some backup devices will show their
storage based upon a 2:1 compression. For example I use a HP 24GB DAT DD3 tape drive.
Uncompressed it only holds 12GB. However, the tape drive compresses data automatically in
the electronics on the drive. When choosing backup devices is a good idea to choose a
device that compresses data automatically because the computer doesn't have to do it so the
backup process is faster.

--
Dave




"Vic" wrote in message
...
| David, what a great explanation. I appreciate the detail, it really help me understand the
difference between backups and imaging.
|
| One question still remains, is an image 'smaller' in size than the information it 'snap a
shot' of (i.e. is an image COMPRESSED
| information)?
|
| TIA
| Vic
| ___
| "David H. Lipman" wrote in message
...
| Disk imaging is the process where the admin. runs software, outside of the Operating
System
| like booting DOS from a Floppy Disk, and creates an image of the entire hard disk. It
is a
| "snap shot" of the system at the point the system was imaged. The image could be a
series
| of disk files, stored on a Tape Drive, CD disks, DVD media, ZIP disks, etc. Using
software
| files can be extracted individually or enmasse from the image.
|
| Using the software an image can be made and restored to a hard disk that isn't even
| formatted. For example, lets say that an OS is running with a 20GB hard disk that has
1GB
| free. An image can be made, a 60GB hard disk can be installed and the image restored to
the
| empty hard disk. Now you have the exact same system not with 1GB free hard disk space
but a
| system with 41GB free disk space.
|
| Another example might be I have 10 identical model platforms. Lets say an IBM Thinkpad
| A22m. I can install all the software on one of the notebooks. Completely configure all
the
| software. Depending on the OS, SysPrep the platform. Then an image can be created.
Now
| that image can be restored to the other nine platforms. Note this *only* works with
| identical model platforms. When done, 10 systems will be setup exactly alike.
|
| Two well know imaging packages are Norton/Symantec Ghost and Acronis True Image.
|
| Imaging is more exact that backups. Backups are usually selected data but can be an
entire
| system. However, a backup will only copy data files on a hard disk. It will not create
a
| representation of the hard disk's partition table or file system. In the example above,
if
| an image is made of a Win2K platform using NTFS, the image can be restored to an bare
hard
| disk and the final object will be Win2K on NTFS. Another difference is that the backup
| software usually runs under the OS. When this is done, programs and the Operating
System
| will hold File Handles open. This can be a hindrance to both backing those files up and
| restoring them. This can be overcome by using a backup application that can be executed
| outside the OS like off a floppy disk. However, to restore the files to a hard disk,.
the
| hard disk must be High Level Formatted.
|
| HTH
|
| --
| Dave
|
|
|
|
| "Vic" wrote in message
| ...
| | Was going through posts in this group and saw a number of comments on 'disk imaging'.
I've
| heard of 'imaging' from years back but
| | never understood what it is, or how someone can take an 'image' and restore all their
data
| from an image to another drive. To me
| | imaging sounds like backing-up information, yet a disk image sounds very small in size
| compared to a backup.
| |
| | Would is the difference between imaging and backing-up?
| | What is 'imaging'?
| |
| | Thanks,
| | Vic
| |
| |
|
|
|
|


  #6  
Old February 1st 05, 02:16 PM
Lil' Dave
external usenet poster
 
Posts: n/a
Default

"Vic" wrote in message
...
Was going through posts in this group and saw a number of comments on

'disk imaging'. I've heard of 'imaging' from years back but
never understood what it is, or how someone can take an 'image' and

restore all their data from an image to another drive. To me
imaging sounds like backing-up information, yet a disk image sounds very

small in size compared to a backup.

Would is the difference between imaging and backing-up?
What is 'imaging'?

Thanks,
Vic



"Backup" is a very loose term that may or may not be used to describe an
image process. However, in the strictest terms, backup is a filesytem only
backup. It may be a simple copy using explorer or the dos copy command or
similar, or it can be an actual backup application that may or may not
compress all the files into one or more files. Only the backup program can
restore that backup file(s). In restoration, the user must create an
adequate sized partition to restore those files. The partition must be
active and primary if the backup restoration is an operating system. Any
partitions created for purpose of file restoration must be formatted by the
user first. In many cases, the boot files are not restored to the proper
locaton of the hard disk active partition and the system cannot boot as a
result. The user has to go to further action to place these file in the
proper location, usually using the sys command. If the backup application
can only operate in a windows environment, windows and the backup
application must be installed before restoration.

Imaging copies the master boot record, partition boot records and other
partition information, and copies the filesystem. and the files themselves.
Imaging natively "compresses" files as it does not copy file slack. The
filesystem uses clusters, in most FAT 32 cases, 4KB clusters to store files.
If a file is of 5KB size, 3KB of a cluster will not be used. This is called
file slack. Imaging programs can also further compress this image data.
Restoration is straightforward and uses either a boot floppy diskette(s) or
boot CD to operate from.if restoring an operating system partition to a
blank hard disk. That is, it operates totally independent of the hard disk
current contents. Image restoration of a non-boot partition can occur in a
windows environment. Imaging may occur in windows or in an msdos
environment, so windows is not a requirement of the original image. The
benefit of an imaging is that the user does not have to go through the
laborious process of creating the partitions and filesystems (formatting)
before restoration. XP imaging is similar, but real-time imaging of the
operating system partition can occur in that environment using imaging
programs developed for that environment.

Typically, an image file will use approximately 60% of space formerly
occupied by the same files in a given partition. This depends on the size
of the files to begin with, and their corresponding file slack. And, again,
this can be further compressed by the imaging program. This depends on the
compressability of the file(s). As an example, zipped files and the like
are less likely to compress an appreciable amount, whereas, text files will
allow much compression. Compression requires more time for the image to
create, less compression less time.

Do not defragment a partition containing an image file(s). Leave it be.



 




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