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Chapter 3:
Using Norton Ghost
Image files and CRC32
Cyclic Redundancy Checking (CRC) is a data error checking technique.
CRC ensures that the original data that was written to the image file is the
same as the data that is being used from the image file. The 32 value in
CRC32 indicates the CRC technique uses a 32-bit value to store error
checking information. The use of CRC32 increases detection of errors in
the image file.
When image files are created, CRC32 details are embedded into the file to
ensure image file corruption can be detected when it is being restored to
disk. CRC32 is currently included on a file-by-file basis with FAT partitions
and on a MFT table basis for NTFS partitions.
In addition to image file error detection, the CRC values can be used to
verify that image files and partitions or disks are identical. This can offer an
additional detection method against bad sector writes and other drive
anomalies that may be missed during normal imaging checks.
A text file containing CRC values and associated file attributes can be
generated using the -CRC32 command-line switch. These switches and
functions are detailed in Appendix A.
Image files and volume spanning
Standard image files
Standard image files consist of a single file that contains the contents of the
complete disk or required partitions. This type of image file is used for
storing system configurations on hard disk drives and tape drives where
the volume is large enough and capable of holding the complete image file
in one piece.
Size-limited, multi-segment image files
There are situations where it may not be practical to have a standard image
file. Norton Ghost can split up an image file into segments (known as
spans) that are limited to a user-specified size. This option is most
commonly used to limit span sizes to 550 MB for later transfer onto CD.
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