Compression algorithms speed and ratio comparison.

[lopi]

I've tested all compression algorithms availible in Clonezilla (I skipped non-smp versions if smp version was available). Here are the results:

param	type	save (min)	restore (min)	image size (mb)
-z1p	parallel gzip	4.9	2.2	6916
-z2p	parallel bzip	6.4	2.1	5915
-z3	lzo	5.4	2.1	8300
-z4	lzma	>1h, too long
-z5p	parallel xz	14.2	2.1	5208
-z6p	prallel lzip	15.4	2.2	4949
-z7	lrzip	failed
-z8p	parallel lz4	4.2	2.0	8259
-z9p	parallel zstd	3.5	2.0	6106

My setup: 1 Gbps network, Clonezilla SE in virtual machine on pretty old server, and fast client PC with Core i5 processor. Clean Windows 7 with browser, totalling 20GB, was used for cloning purpuses.
For me parallel zstd (pzstd) is definetly a winner: it shows best save and restore times and pretty decent compress ratio, and also it's very CPU efficient, so it won't be slow on older PCs and saves your power bill.
I really think that pzstd must be default compression tool in Clonezilla. And may be instead of algorith give abiltiy to user to choose zstd compression level.

[Steven Shiau]

Thank you for your feedback. Yes, I believe zstd is bettern than gz. However, since gz is more common, and there are more utilities about it, like gzrt which can help to recover the broken file about gz. Therefore for the moment we'd like to keep gz as the default one. In the future, we might switch to zstd, as you have suggested.
Thanks again.

Steven