Posted 19 May 2010 - 10:25 PM
I noticed how poor the compression of wim images is compared to other archives.
original NaughtyPE folder - 100%
wim - 54%
zip - 51%
7zip - 39%
From what i've read, wim uses the LZX compression algorithm. Would it be possible to switch it out for something, which delivers more bang for the buck? Like the algorithm used in 7zip?
Posted 19 May 2010 - 11:10 PM
Posted 19 May 2010 - 11:26 PM
But since we have now a Win2k3 Bootloader, which supports wim booting unlike the original, i don't think the patching is the problem.
The question is, is it even possible to use such a high compressing algorythm in a wim or is there a reason wim do not perform better?
Posted 19 May 2010 - 11:41 PM
Posted 20 May 2010 - 10:18 AM
Posted 20 May 2010 - 10:48 AM
I used the wimboot script from LiveXP to create the wim, the setting was maximum.
You haven't mentioned anything about a script, so I don't know what you're meaning.
The setting for all Archivers was Best, but not solid.
Posted 20 May 2010 - 09:54 PM
That's about what I would have expected. WIM compresses better than ZIP. WIM will come down considerably if there's duplicate files.
Posted 20 May 2010 - 11:00 PM
Still a 7zip compression would get it down an additional 10%. Giving it a compression ratio of 2,5.
That wim save a lot of space, when files exist more than once, does unfortunately not help with bootable wim like in our case, there are no duplicate files.
Posted 20 May 2010 - 11:17 PM
Regarding using a new compression algorithm in WIM images, one important issue you'll need to confront is getting such an image mounted to the file system as current WIM images do. Sure, compression with 7z will be smaller, but will there be a performance hit with read-write access vis-a-vis the current algorithm? With 7z I strongly suspect there would be as its designed for compression, not as a potential container for a booting PE.
Posted 21 May 2010 - 07:05 AM
or a similar thingy.
As Galapo said, most compression algorithms have an inefficient indexing even for reading, let alone for writing:
Why CFS instead of ZIP
The ZIP format is a staple format used in many applications. All modern operating systems have some form of integrated support for ZIP files. For many applications ZIP is certainly the right choice over CFS or ISO.
ZIP does have its limitations including:
Poor randam access performance in large compressed files due to lack of compression indexing.
Poor compression performance in archives with many small files due to file based compression.
File based password protection and encryption.
Introduction of essentially proprietary compression algorithms, encryption, and other extensions.
ZIP is targeted by many firewall and e-mail filtering applications, making it increasingly difficult to use for file transfers.
Why CFS instead of TAR, RAR, 7Z, etc
Most archive formats do not consistently provide the compression indexing necessary to allow efficient random access. This makes archive formats inefficient or unusable in file system related applications.
The data format and compression algorithms used in the RAR format are not freely available for use in other applications.
The 7Z archive format is documented, but available implementations of the numerous necessary compression algorithms have restricted licensing.
It's mostly a trade-off:
tight compression vs. acessibility/processor power
Try KGB to have an idea of what I mean:
Compare first programs in "tightness":
with those in "speed":
BTW, FREEARC is not too shabby:
Posted 21 May 2010 - 10:17 AM
The way the WimBoot.script works, is the wim protected or made writable by means of fbwf.
Thus it wouldn't matter, how long the compressing takes. This is only done during build.
However a fast random read access would be required and here helps that the boot.wim is always a ramdisk, imo.
Solid archives - archives without random access are a no-go for sure.
Lots of nice reading. Thanks you.
Yep KGB is a bitch, got stuck with one of those archives once on an, at the time, outdated system. 14 hours decompression!
btw. Think i possibly found the reason for the poor performance of wim compared to the other archivers, from what i've read, it seems, that all the compressors, which work better than wim, use more than 1 algorythm to compress files. Could not find any such description for wim.
If this is right, improving might not be possible.
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