Compression option z9p, can we tweak the compression ratio

[Harry E]

Hello:

Question: Is there a way to increase the compression ratio of z9p to generate a smaller backup file?

My situation: I backup my hard drive using Clonezilla live. I specify z9p as the compression option. Based on the size of the backups, my backup medium has space for 2 backups. If the backups were slightly smaller (about 10%) I could fit 3 backups on the backup medium.

I ran tests using other multi-core compression options. The results were unsatisfactory because the backup files were larger or the runtimes were much greater than z9p.

I browsed drbl-ocs.conf and I noticed the following comment at line 98:

-1 (fastest), -2 ... -9 (best compression)

There were several statements in the following lines that pertained to z9p:
extra_zstd_opt="-3"
extra_zstd_opt_onthefly="-3"
extra_zstdmt_opt="-3"
extra_zstdmt_opt_onthefly="-3"

I ran tests in which I entered higher values for these options but there was no change in runtime or size of the backup files.

Is there a way to increase the compression ratio of z9p to generate a smaller backup file?

Thanks

[Cristian STANESCU]

Hello. I have tested at some time a program similar to Clonezilla, named RescueZilla. It can tweak the compression ratio (up to "z19p", which means maximum compression - but beware of the time it will take, far longer than "z9p"; the difference was that an 11GB backup made with Clonezilla had only 9GB when I made it with RescueZilla and maximum compression, "z19p" - but it took 2 hours, not 5 minutes like Clonezilla).
Please note that RescueZilla does not have the posibility to clone over a local network multiple computers at once! It only works locally, only on one computer at one time!
Also note that RescueZilla is not "fully interoperable with Clonezilla" as it states! That is not true! I have tested it and it is not true!
I could recommend you another tool, which has Clonezilla included (but please note that backup made with different Clonezilla versions are not necessarily compatible - the may not work and I had this problem when testing the following tool): Q4Rescue - please search for it with Google.

With Q4Rescue I managed to browse the web, read and write e-mail while the computer was restoring a clone backup with Clonezilla in a terminal window!! But Q4Rescue offers many utilities like GParted or HDSentinel.

[Cristian STANESCU]

I forgot to add that I have decided to stay with the industry standard Clonezilla!! :-)

[Harry E]

Hello Cristian

Thanks for the information about Rescuezilla.

I downloaded Rescuezilla and tested it. As you wrote, it allows the user to adjust the compression ratio used when performing a backup. This is what I was looking for.

Thanks

[Harry E]

Update
For Clonezilla live, the parameters that set the compression ratios are in the following config file:

/etc/ocs/ocs-live.conf

The values run from -1 (least compression) to -9 (highest compression). However, Z9 has a range of -1 thru -19.

To modify the values, do the following:
1. Boot Clonezilla live.
2. Go past the windows that deal with language and keyboard. On the window that says 'Start Clonezilla' choose 'Enter shell' and then click OK.
3. At the command prompt type
sudo nano /etc/ocs/ocs-live.conf and press enter
4.Make your changes. Then press control-O to save the changes, then control-x to return to the command prompt.
5. Type sudo clonezilla and press enter to start clonezilla

See the following wiki page for more information:
https://deepwiki.com/stevenshiau/clonezilla/6-advanced-usage

[Steven Shiau]

Yes, /etc/ocs/ocs-live.conf has higher priority than /etc/drbl/drbl-ocs.conf when running in Clonezilla live. Hence the file you edit should be /etc/ocs/ocs-live.conf.