Time to mark this one as solved, I guess. I marked Dzsono's suggestion as the solution, since I tried PeaZip and decided to use it from now on. I think it inherited IZArc's place as my universal Windows archiver utility for now.

I use mostly the 7z algorithm with it I guess. Maybe its proprietary pea-algorithm is also good, but I'd rather stick to more widely used formats (except for maybe temporary use).

God damn it. What's with 7-zip? Every now and then, it just seems to decide to make a corrupted archive when you are compressing something, not even notifying the user there is a problem.

Again yesterday, I compressed the Strategy First bundle's "Jagged Alliance 2 Gold" installation file subdirectory into a less than gigabyte .7z file. I also did that to a bunch of other games in that same bundle, separate 7-zip file for each.

I ran the compression test for the compressed files, and sure enough, others passed, but JA2 Gold 7z file reported a CRC problem. I compressed it again, and this time test completed ok for it too.

So it seems that if I am going to use 7-zip, I really have to routinely run the internal test for each compressed file right after the compression, just to check if I need to do it again. And there is no indication why, and when, it creates corrupted compressed files.

God damn it, I'm thinking of installing WinRAR, I don't recall running into similar problems with it on this same PC. It always seemed quite dependable.

That does it. For some reason 7-zip feels quite unreliable for me. Quite frequently, when I try to make big (gigabyte size) 7z archives, they are corrupted at least on the first attempt. I have no idea if it is due to 7-zip, or if there is something wrong with this machine, but at least a memory test nor HDD test didn't find anything wrong with RAM nor HDD.

I'm taking WinRAR into limited use now, and see if it works reliably for me. At least it used to in the past. Still hoping for a reliable freeware/open source solution (which supports multipart archives), though.

In case it works reliably. I would even pay for WinRAR, but then I'd have to apparently pay $23 for _each_ separate PC I am using, in order to WinRAR on all of them? I have like four PCs in semi-active use at the moment, so... Or do I just misunderstand RARlabs pricing? Maybe I need to contact them.

I did, but I had pretty much the same issue with it, at least when using 7-zip algorithm. So I swapped it for the official 7-zip utility.

Maybe true, but a bit beside the point I think. I want the compressor utility to be reliable, no matter what I compress with it.

But since I don't see many others reporting similar problems with 7-zip, it could still be something with my PC. Or, I am using 7-zip wrong, or something. But I'll test WinRAR for now. I don't like using WinRAR though, as it is as proprietary as it gets. Since I'm also using Linux etc.

What I'm saying is that if you're only getting 1 or 2% compression you're incurring an additional risk of file corruption with little or no benefit and as such it's probably better to just split the file.

But, you are of course right, if you're going to compress something then you should be able to count on it having been compressed correct. To suggest otherwise would be stupid.

I don't know if I should be relieved or annoyed, but at least so far WinRAR has worked 100% reliably for me, in those situations where 7-zip or PeaZip (with 7-zip format) would quite often produce corrupted archives.

So apparently it is not something on my machine (like faulty RAM causing data corruption, or virus scanner interfering with the compression utility), but something inherent with 7-zip.

Too bad I don't want to use WinRAR too much as I use many machines, some of which run Linux. So I'd really prefer a cross-platform open-source solution with multipart compression support, and 7-zip seemed to fit the bill perfectly.

I'd love to get back to 7-zip, if:

- they fix the reliability problems, or I find out why I am having these problems with it

- it wouldn't hurt if they added two options from WinRAR to 7-zip too: "test archived files" (after compression) and "put recovery record". That way at least I wouldn't have to test the archived files manually after the compression.

The "test archive" feature is already there. It's just that it is only accessible through the shell context menu, for some reason.

EDIT: Oh, it's in the toolbar, too. The light blue arrow pointing downwards. I have the toolbar turned off because it's so damned ugly.

I meant that it would test the integrity of archives automatically after creating each archive, without me having to run the test manually for the archives afterwards in order to find out whether the process was successful. At least I didn't see this in the options, but maybe I missed it. WinRAR has this "Test archived files" checkbox, when you are readying to create an archive.

Offtopic: Woohoo, GOG fixed the editing function!

I see. You're right, I don't think you can do that.

Oh, finally.

Did you end up using PeaZip then? I think I should switch to it too, I prefer applications that are open source and all around (like support of many formats).

As said, I had reliability problems with both PeaZip (when using it for creating 7-zip archives) and the official 7-zip utility. With big gigabyte size archives, for some reason both seem to occasionally create corrupted archives for me, maybe 20% of the time.

So far I haven't faced the same with WinRAR on the same PC even when creating solid archives with the best compression, but then I'd rather not use WinRAR as it is a proprietary format. Linux etc...

Other than that, PeaZip was pretty much perfect, very close to WinRAR. I didn't try PeaZip's own "pea" format, I rather use some widely used format like 7-zip. PeaZip feels a bit better utility than 7-zip, with a few more options and such, but 7-zip is almost the same.

PeaZip's own format seems great, it's made for security and effeciency reasons.

I'm curious. Of all the backups you have now made (it seems a lot if you have up to a couple of gigs or more) how much space did you save? The compression ratio basically.