4 ms·

The ISO images are compressed with RAR. What a bizarre choice.

by jwilk 7y ago

asveikau 7y ago
It is weird, in part because iso has directory entries, and so does rar. Iso.gz or iso.xz seems like it would make more sense, eg. a block compressor. But something like OS install media I would expect to already have compression applied to payload. Eg. Rpm and deb files probably use gzip. That wouldn't compress too well. So maybe just .iso would be fine. Rar itself seems to be pretty common in certain enthusiast communities where people tend to use windows. For example I still see it when people are passing Android ROMs and unlocking tools around on web forums. And very few other places.
- linuxuser001 7y ago
  I'm curious because I'm trying to convince people to switch from .rar to .tar.gz at work, wonder if you know the benefits, what does it mean that one is a block compressor?
  - chungy 7y ago
    Generally speaking, there's two large categories of archivers in competition with one another: 1. Efficient random-access storage. If compression is supported, it is done on a per-member database. 2. Efficient all-at-once compression (block/solid compression). This is either handled explicitly by file format (RAR and 7z, for example), or the archive doesn't support compression (tar) and itself is processed through an external compressor. On the first category, I would argue Zip has clear superiority over most other file formats. It supports all metadata fields for both DOS/Windows and Unix operating systems, and has very wide support amongst everything. Zip does not support the second category of archival formats. In the second category, 7z (I don't know about RAR, but I suspect it holds true) only supports DOS attributes and modified dates, making it totally insufficient for backing up a lot of kinds of Unix file trees. tar is generally the de facto standard for Unix and naturally supports all metadata. I would argue gzip is long obsolete; zstd is much faster (it can nearly compete with xz too for file size). tar files don't really support random access for individual members, lacking a central directory, though uncompressed files can be seeked rather rapidly anyway as the tar program just skips over members (each member encodes its length). Compressed tar files make this worse, since the entire archive must be uncompressed in memory just to find anything. This is a large reason that tar is mostly restricted to being used when extracting individual members is not a generally useful operation. If that is a useful operation in your datasets, go for Zip.
    - genpfault 7y ago
      RAR also has built-in forward error correction, something I sorely miss with 7z :(
chungy 7y ago
I didn't even know RAR was still around/used.
- japanoise 7y ago
  It's pretty popular in more casual circles. I'm pretty sure it's still the chosen format for videogame mods and the like
  - flatiron 7y ago
    It’s the default for piracy too
  - sneakernets 7y ago
    Off the top of my head: * Some VGM formats (game music) are compressed with rar * Certain 90s game mods are compressed with rar * Lots of pirated/cracked games are compressed with rar The main reason I've been told as to why this is seems to be the extensive error correction, which was a big deal with large game files back in the Dial-Up/ISDN days where a corrupted download was more common than now, and old habits die hard.
    - deleted 7y ago
      [deleted]
bbanyc 7y ago
Certainly bizarre. Among other things, almost none of the archived distros can read the RAR format. It's weird, come to think of it, that RAR has existed for a quarter of a century, and yet the format has never been documented or reverse-engineered and no FOSS implementations exist. The only way to make a RAR file is the official program, which is binary-only shareware; there is public source code for extracting RARs but under a license that explicitly forbids using it to reverse-engineer the format. But I guess the overlap between people who care about all that and people interested in the kind of stuff RAR is used for is next to minimal.

The ISO images are compressed with RAR. What a bizarre choice.

by jwilk 7y ago

The ISO images are compressed with RAR. What a bizarre choice.

It is weird, in part because iso has directory entries, and so does rar. Iso.gz or iso.xz seems like it would make more sense, eg. a block compressor. But something like OS install media I would expect to already have compression applied to payload. Eg. Rpm and deb files probably use gzip. That wouldn't compress too well. So maybe just .iso would be fine. Rar itself seems to be pretty common in certain enthusiast communities where people tend to use windows. For example I still see it when people are passing Android ROMs and unlocking tools around on web forums. And very few other places.

linuxuser001 7y ago
I'm curious because I'm trying to convince people to switch from .rar to .tar.gz at work, wonder if you know the benefits, what does it mean that one is a block compressor?
- chungy 7y ago
  Generally speaking, there's two large categories of archivers in competition with one another: 1. Efficient random-access storage. If compression is supported, it is done on a per-member database. 2. Efficient all-at-once compression (block/solid compression). This is either handled explicitly by file format (RAR and 7z, for example), or the archive doesn't support compression (tar) and itself is processed through an external compressor. On the first category, I would argue Zip has clear superiority over most other file formats. It supports all metadata fields for both DOS/Windows and Unix operating systems, and has very wide support amongst everything. Zip does not support the second category of archival formats. In the second category, 7z (I don't know about RAR, but I suspect it holds true) only supports DOS attributes and modified dates, making it totally insufficient for backing up a lot of kinds of Unix file trees. tar is generally the de facto standard for Unix and naturally supports all metadata. I would argue gzip is long obsolete; zstd is much faster (it can nearly compete with xz too for file size). tar files don't really support random access for individual members, lacking a central directory, though uncompressed files can be seeked rather rapidly anyway as the tar program just skips over members (each member encodes its length). Compressed tar files make this worse, since the entire archive must be uncompressed in memory just to find anything. This is a large reason that tar is mostly restricted to being used when extracting individual members is not a generally useful operation. If that is a useful operation in your datasets, go for Zip.
  - genpfault 7y ago
    RAR also has built-in forward error correction, something I sorely miss with 7z :(

chungy 7y ago

I didn't even know RAR was still around/used.

japanoise 7y ago
It's pretty popular in more casual circles. I'm pretty sure it's still the chosen format for videogame mods and the like
- flatiron 7y ago
  It’s the default for piracy too
- sneakernets 7y ago
  Off the top of my head: * Some VGM formats (game music) are compressed with rar * Certain 90s game mods are compressed with rar * Lots of pirated/cracked games are compressed with rar The main reason I've been told as to why this is seems to be the extensive error correction, which was a big deal with large game files back in the Dial-Up/ISDN days where a corrupted download was more common than now, and old habits die hard.
  - deleted 7y ago
    [deleted]

bbanyc 7y ago

Certainly bizarre. Among other things, almost none of the archived distros can read the RAR format. It's weird, come to think of it, that RAR has existed for a quarter of a century, and yet the format has never been documented or reverse-engineered and no FOSS implementations exist. The only way to make a RAR file is the official program, which is binary-only shareware; there is public source code for extracting RARs but under a license that explicitly forbids using it to reverse-engineer the format. But I guess the overlap between people who care about all that and people interested in the kind of stuff RAR is used for is next to minimal.