It may not be a problem of Keka, but 7-Zip about large folder compression

[SkyKiDSkr]

Greetings, Kekarians(Keka users)! :)

I found a bug(?), when trying to compress the large folder(> 100GB) with full CPU threads, it takes long long time or failed to compress. I wrote a draft with bug report format, but it is not a bug of Keka but 7-Zip, I think, and I am not familiar with "Issues" and "GitHub", so leave it here.

Description

I made my iPhone backup with encryption by an official method of macOS, and a folder was created at /Users/_[my id]_/Library/Application Support/MobileSync/Backup/. The folder size is larger than 100GB(114.75GB).

I used Keka to compress it with options below,

• Format: 7z
• Compress ratio: slowest, highest compression(right end of the bar)
• Solid compression
• Do not include Mac resources like .DS_Store

Keka seemed to compress it, the progress bar was not growing however and the estimated time got bigger continuously(3-4 DAYS). So I cancelled the job.
Tomorrow, I try the same task with the options above plus new one, "Maximum threads limit to: 6", then it is completed in 3-4 HOURS, What...?

Configuration

• Keka version: 1.6.7 (5729)
• macOS version: 26.5.2(25F84)

Conditions

• Mac mini(M1, 2020) with 16GB RAM
• Running applications: Chrome to watch some videos at Twitch, Chzzk and YouTube, Keka, Parsec(only daemon) and some system processes and apps

Korean

macOS 공식 기능으로 만든 100GB가 넘는 내 iPhone 백업 폴더를 Keka를 이용해서 7z 압축을 시도했는데, 예상 시간만 3-4일까지 늘어날뿐 완료를 할 수 없어서 취소했다. 며칠 후 똑같은 작업을 최대 CPU 스레드 제한을 6으로 하고 시도했는데 이번에는 불과 몇 시간 만에 작업을 완료하였다. 이것은 Keka의 문제가 아닌, 7-Zip의 문제가 아닐까 생각한다. 그래서 버그 리포트용으로 만든 초안을 여기에 수정하여 올려본다.

[gingerbeardman]

The backup is probably already compressed, it's worth checking before hand.

I would not recommend trying to compress this sort of data.

100GB is a lot of data, it will take a long time to compress, even on the lowest compression.
On highest, I'm surprised it was as quick as a few hours!

Also, how much disk space do you have available? Around an additional 100GB?

When it fails, please post the error message.

[SkyKiDSkr]

I didn't know that the backup had been already compressed. I want to move it to another storage actually, and hope to shrink its size.

Well, the SSD of Mac mini has less than 100GB available(95GB, I think), so made Keka compress to a portable HDD.
And there was no error message because I cancelled the job with full CPU thread. haha...

It is curious when using less CPU thread than full, the job is completed, but full it can't be.

[gingerbeardman]

Additional bottleneck will also be the connection to portable HDD, because the data has to go back and forth across the wire.

It is curious when using less CPU thread than full, the job is completed, but full it can't be.

This is most curious. Maybe the system kills a long-running app using full CPU?