Ghost compression ratios and performance

Article:TECH106775  |  Created: 1999-01-16  |  Updated: 2013-10-30  |  Article URL http://www.symantec.com/docs/TECH106775
Article Type
Technical Solution

Product(s)

Environment

Issue



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


Solution



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. Any particular Ghost operation may have times and speeds that differ considerably from those shown in the test situations that follow.


Differences by Ghost version
  • The version of Ghost.exe that is included in Symantec Ghost 7.0 and later has changes that significantly improve performance in some common situations but do not improve performance in all common situations.
  • For the high and very high compression levels, Ghost 5.1c is improved over Ghost version 5.1b and earlier.


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, Ghost.exe and Ghostpe.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 transfer rate. The High level provides a higher compression level, but it has a slower transfer 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 DOS command line to use to compress the image file:

Ghost.exe -Zn

OR

Ghostpe.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.


Testing
Symantec tested Ghost to determine how much compression was achieved with the different Ghost compression levels and how the chosen level affected Ghost's performance.

Though these tests were done on computers that were typical at the time of the tests, your results are likely to vary. The following figures are approximations of how Ghost might perform in many situations, but some situations may differ considerably from these figures.

Symantec Ghost on Windows XP Sample:


Compression level

Image size (megabytes)

Backup (Disk-To-Image)

Restore (Image-To-Disk)

Compression ratio



Time

Time as a percentage of the base

Time

Time as a percentage of the base


None (base)

1,065

5 minutes 27 seconds

100

9 minutes 4 seconds

100

100

Fast (low)

725

5 minutes 4 seconds

93

7 minutes 29 seconds

82

68

High

620

7 minutes 57 seconds

131

8 minutes 6 seconds

89

58

*Very high

600

12 minutes 49 seconds

158

7 minutes 59 seconds

88

56

*Very high compression corresponds to the -Z9 command line switch.

These tests were done using Symantec Ghost 7.5 and a Windows XP NTFS partition. The computer was a Dell Optiplex GX1 P3 450. The source disk was a 4 gigabyte SCSI IBM DDRS-34560DD. The destination disk was a 4 gigabyte IDE Samsung VA34323A. The source disk contained 1.065 gigabytes of data.

Norton Ghost 5.1c

Compression
level
Backup (Disk-To-Image)
Restore (Image-To-Disk)
Size of image
Time in seconds
Time as a percentage of the base
Time in seconds
Time as a percentage of the base
Bytes
Compression ratio
None (base)
223.88
100%
235.46
100%
642,819,211
100%
Fast (low)
253.49
113%
233.66
99%
452,547,427
70%
High
380.08
170%
248.82
106%
388,083,722
60%
*Very high
679.43
303%
247.05
105%
376,439,931
59%

*Very high compression corresponds to the -Z9 command line switch.

These tests were done using Ghost 5.1c and a Windows 98 FAT32 partition. The system had the Windows 98 Plus Pack and Office 97 installed. Ghost ran under Windows 98 on a Pentium II 400 MHz computer. All operations were disk to disk on local IDE disks.






Legacy ID



1999021610150425


Article URL http://www.symantec.com/docs/TECH106775


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