Cypher Technology Ltd V2.6 (03) December 2011
17
5.1.1
Full Image Master
“Full Image”. This is the format originally used within PUMA. The Full Image Master
contains a single file called “flash.img” which is a bit for bit copy of the whole of the flash
card. It is the same size (in Kbytes) as the flash card. The flash.img file has its time
created, modified and accessed values set to the time of the start of the transfer. This
time is taken from the system time as displayed on the front panel of the machine at
start-up.
When the flash card is bigger than the disk size, multiple disks are needed and each
disk will contain part of the image. The first disk will contain a file called flash1.img , the
second disk, flash2.img etc. These part images may be combined to form a single,
complete image file (see Section 4.5.3 ).
The Master Copy can be used in two ways. On a PC with an Image Viewer program or
by restoring the image back to a flash card or USB disk.
5.1.2
Compact Master
The “Compact” format was introduced in V2.2 and has two advantages over the Full
Image Master:
•
Files may be accessed directly in the Files folder
•
Blank portions of the card are compacted: a wiped card, with only a few MBs of files
creates a Master of only a few MBs.
5.1.3
The Compact Master process
First the FAT file system on the flash card is analysed for any errors. If errors are found,
this is not a problem for the back-up and the user is not notified. It does mean that the
file data cannot be used to create the Master and the whole card is treated as the
unused portion of the card. Files are not copied to the Master as actual files but as
image data.
If the file system is good, the FAT can be used to calculate the location of the file data
on the flash card. The files are copied from the flash card into the “Files” folder on the
Master disk. Having copied all the files, PUMA then scans the unused portion of the
card (i.e.the area of the card not used by the files) and copies any meta data, deleted
files or file fragments to the Master. This data is stored in Image files named
Image_data0.dat, Image_data1.dat etc in the “AuxData” directory on the Master. An
“Image_data.xml” file is also created in the AuxData directory and this records where
the data in the files was stored on the flash card. This allows the original card to be
precisely cloned during the Restore or Checksum processes.
A checksum is produced at the end of the disk creation. This is the checksum of all the
data (files and any meta data) on that disk.
If the files and meta data are greater than the disk capacity, PUMA will prompt for
further disks. These The checksum of each intermediate disk is displayed after each
disk has been verified. When the Master set is complete, a further checksum is
displayed, which is the sum of the individual disk checksums. This checksum is the
same as the checksum of the flash card, as it is produced from the same data.
The Files folder may be accessed from a computer file browser in the usual way. Third
party data recovery tools can be used on the Image files to, for example, recover JPEG