dwarfs-0.5.6

Bugfixes

• Build fixes for gcc-11 (fixes #52)

• Use REALPATH in version.cmake to fix building in symbolically linked repositories (fixes #47).

dwarfs-0.5.5

Features

• If a filesystem block cannot be compressed to less than the uncompressed size, it will be stored uncompressed. This feature actually fixes the bug described below.

Bugfixes

• When building a filesystem from high entropy input data (e.g. already compressed files), and when using LZMA compression with block sizes >= 25, the LZMA algorithm could be unable to pack a block into the worst-case allocated size. This behaviour was not expected and crashed mkdwarfs, and seems to me like a bug in LZMA's lzma_stream_buffer_bound() function. The issue has been fixed by not compressing blocks at all if the compressed size matches or exceeds the uncompressed size. This fixes part of github #45.

• Filesystems created such that after segmenting the total data size was a multiple of the block size (i.e. the last block was completely filled) had the last block written to the image twice. Such a filesystem image is perfectly usable, but the repeated block uses space unnecessarily. This is highly unlikely to happen with real data.

• Filesystems created with -P shared_files, but no shared files in the source tree, were created correctly, but could not be loaded. This has been fixed and the filesystems can now be loaded correctly.

Other

• Added tests for binaries and FUSE driver.

• Minor code cleanups.

dwarfs-0.5.4

Bugfixes

• FUSE driver hangs when accessing files and the driver is not started in foreground or debug mode. This bug is present in both the 0.5.2 and 0.5.3 releases. Fixes github #44.

dwarfs-0.5.3

Bugfixes

• Add PREFER_SYSTEM_GTEST for distributions (like Gentoo) that have a gtest package. (fixes github #42)

• Make sure the source tarball can be built inside a git repo. The version file generation code would attempt to pull information from any outside git repository without checking if it's actually the DwarFS repo. This issue came up when building Arch Linux packages.

dwarfs-0.5.2

Bugfixes

• Make FUSE driver exit with non-zero exit code if filesystem cannot be mounted. Fixes github #41.

dwarfs-0.5.1

Bugfixes

• fsst library was built with -march=native, which caused the static binaries not to work on non-AVX platforms. The fsst library is now being built with no extra flags.

dwarfs-0.5.0

New Features

• New metadata format (v2.3). This includes a number of changes:

  • Correct hardlink preservation. With older metadata formats, all duplicate files would appear hardlinked. The new format preserves hardlinked files exactly as present in the input data, and performs additional deduplication at a lower level.

  • The new format offers a lot of customization for additional packing of metadata. You can use these to trade off metadata size, mounting speed, etc. Especially for filesystems with millions of files, the metadata size can be reduced significantly.

  • In particular, filename and symlink data can be stored in a format that reduces the size by roughly a factor of two, but still allows for random access, so the compressed data can be mapped into memory and decompressed on the fly.

• DwarFS now directly supports images using a custom header. The header can be completely arbitrary. mkdwarfs can write, replace or remove such headers, and all other tools can either skip to a specified offset, or determine this offset automatically. This fixes github #38.

• dwarfsck has been improved to perform extensive metadata checks.

• dwarfsck now shows a detailed breakdown of metadata memory usage, which can be used to optimize metadata packing options.

• Added ENABLE_COVERAGE cmake option.

Performance improvements

• Scanning has been significantly optimized and is now up to three times faster on average.

• Digest computation has been parallelized in both mkdwarfs and dwarfsck giving better performance on multi-core systems.

• A set of micro-benchmarks has been added to evaluate the performance of different filesystem operations. This can be build by enabling the -DWITH_BENCHMARKS=1 cmake option.

• Zstd contexts are now reused during compression, which seems to give some minor speedup.

Bugfixes

• Disable multiversioning on non-x86 platforms, which broke the ARM build.

• Due to a bug in the bloom filter code, only half of each 64-bit block in the bloom filter was utilized, which reduced the efficiency of the filter. The bug was spotted thanks to ubsan. With the fixed filter being twice as effective, the default size of the bloom filter has now been halved.

• When exporting metadata using --export-metadata, dwarfsck was not truncating the output file, which could lead to a corrupt metadata export.

Other

• Compatibility testing with older filesystem versions has been improved.

• A new test suite has been added to check detection of corrupted DwarFS images.

• Added some high level internals documentation for mkdwarfs.

• Documented the filesystem and metadata formats.

• Lots of internal cleanups.

dwarfs-0.4.1

Performance improvements

• Binaries built with gcc have traditionally been much slower than those built with clang, but it was unclear why that was the case. It turns out the reason is simply that CMake defaults to -O3 optimization, which is known to cause performance regressions in some cases. The build has been changed to always build with -O2 when doing an optimized GCC build. The Clang build is unaffected. (fixes github #14)

• The segmenting code now uses a bloom filter to discard unsuccessful matches as early and quickly as possible. While this only gives a minor speedup when using a single lookback block, as you increase the number of lookback blocks speed is barely affected whereas before it would slow down significantly. The bloom filter size (relative to the number of values) can be tuned by using --bloom-filter-size, though increasing it any further from the default is likely not going to make a difference.

• nilsimsa similarity computation has been improved to make use of different instruction sets depending on CPU architecture, speeding up the process of ordering files by similarity by almost a factor of 2.

Bugfixes

• [fix] Linking against libarchive was fixed so that it also works for shared library builds. (fixes github #36)

• mkdwarfs didn't catch certain exceptions correctly, which would cause a stack trace instead of a simple error message. This has been fixed.

• The statically linked executables were unable to handle any exceptions at all due to duplicate stack unwinding code. This has (hopefully) been fixed now.

dwarfs-0.4.0

Up to twice as fast and up to 10% better compression

The segmenting algorithm has been completely rewritten and is now much cleaner, uses much less memory, is significantly faster and detects a lot more duplicate segments. At the same time it's easier to configure (just a single window size instead of a list).

As a result, mkdwarfs speed has been significantly improved. The 47 GiB worth of Perl installations can now be turned into a DwarFS image in less then 6 minutes, about 30% faster than with the 0.3.1 release. Using lzma compression, it actually takes less than 4 minutes now, almost twice as fast as 0.3.1.

At the same time, compression ratio also significantly improved, mostly due to the new segmenting algorithm. With the 0.3.1 release, using the default configuration, the 47 GiB of Perl installations compressed down to 471.6 MiB. With the 0.4.0 release, this has dropped to 426.5 MiB, a 10% improvement. Using lzma compression (-l9), the size of the resulting image went from 319.5 MiB to 300.9 MiB, about 5% better. More importantly, though, the uncompressed file system size dropped from about 7 GiB to 4 GiB thanks to improved segmenting, which means less blocks need to be decompressed on average when using the file system.

New dwarfsextract tool

The new tool allows extracting a file system image directly to disk without having to use the FUSE driver. It also allows conversion of the file system image directly into a standard archive format (e.g. tar or cpio). Extracting a DwarFS image can be significantly faster than extracting a equivalent compressed archive.

Options have been cleaned up

The --blockhash-window-sizes and --blockhash-increment-shift options were replaced by --window-size and --window-step, respectively. The new --window-size option takes only a single window size instead of a list. There's also a new option --max-lookback-blocks that allows duplicate segments to be detected across multiple blocks, which can result in significantly better compression when using small file system blocks.

Bugfixes

• The rewrite of the segmenting algorithm was triggered by a "bug" (github #35) that caused excessive memory consumption in mkdwarfs. It wasn't really a bug, though, more like a bad algorithm that used memory proportional to the file size. This issue has now been fully solved.

• Scanning of large files would excessively grow mkdwarfs RSS. The memory would have sooner or later be reclaimed by the kernel, but the code now actively releases the memory while scanning.

• The project can now be built to use the system installed zstd and xxHash libraries. (fixes github #34)

• The project can now be built without the legacy FUSE driver. (fixes github #32)

dwarfs-0.3.1

Bugfix release

This fixes a couple of minor compilation issues mostly related to issue #31.