You want to know how much compression can be expected from the various Ghost compression levels and how those levels affect Ghost's performance.

The degree of compression and performance are affected by many factors such as the type of data, the make and model of the computer, the bus speed, the type and speed of the hard disk, and other devices on the computer.

Because these factors have a large effect on the degree and speed of compression, actual figures cannot be predicted for any particular situation.

Compression ratio

The amount of compression is measured by comparing the size of the compressed image file to the size of the image file that was created without compression. This figure is a ratio, and is expressed as a percentage. If the ratio is 100 percent, then the size is unchanged.

Compression levels
When you run a Ghost task to create an image file, Ghost32.exe and Ghost64.exe prompt you for the compression level. The two compression levels available through the Ghost user interface are Fast and High. The Fast level provides the lowest compression, however, the image is created faster because it has a faster compression rate. The High level provides a higher compression level, but it has a slower compression rate.

You can also specify the compression level by running Ghost from a command line. Ghost provides nine levels of compression when you use the command line option -Z.

The following is the command line option to use to compress the image file:

Ghost32.exe -Z

OR

Ghost64.exe -Zn

NOTE: Replace n with one of the following options:

• -Z defaults to level 1.
• 1 = Fast. This is the lowest compression level, and the fastest transfer rate (apart from no compression).
• 2 = High compression.
• 3 to 9 = Highest compression level and slowest transfer rate.