COMPRESSION RATIO
-wimlib (and wimlib-imagex) can create XPRESS, LZX, or LZMS compressed WIM
-archives. wimlib includes its own compression codecs and does not use the
-compression API available on some versions of Windows. The below table provides
-the results (file size, in bytes, and time to create, in seconds) of capturing a
-WIM containing an x86 Windows PE image, using various compression types and
-options. When applicable, the results with the equivalent Microsoft
-implementation in WIMGAPI, which is the library used by ImageX and Dism, are
-included.
-
- ===========================================================================
- | Compression type || wimlib (v1.6.1) | WIMGAPI (Windows 8) |
- ===========================================================================
- | None [1] || 531,979,435 in 18s | 531,980,333 in 24s |
- | XPRESS [2] || 207,369,912 in 22s | 209,886,010 in 39s |
- | LZX (quick) [3] || 194,876,901 in 29s | N/A |
- | LZX (normal) [4] || 187,962,713 in 158s | 188,163,523 in 125s |
- | LZX (slow) [5] || 186,913,423 in 358s | N/A |
- | LZMS (non-solid) [6] || 176,880,594 in 182s | N/A |
- | LZMS (solid) [7] || 136,507,304 in 494s | 126,735,608 in 623s |
- ===========================================================================
+wimlib (and wimlib-imagex) can create XPRESS, LZX, or LZMS compressed WIM files.
+wimlib includes its own compression codecs and does not use the compression API
+available on some versions of Windows.
+
+I have gradually been improving the compression codecs in wimlib, and in some
+cases they now outperform and outcompress the equivalent Microsoft
+implementations. Although results will vary depending on the data being
+compressed, in the table below I present the results for a common use case:
+compressing an x86 Windows PE image. Each row displays the compression type,
+the size of the resulting WIM file in bytes, and how many seconds it took to
+create the file. When applicable, the results with the equivalent Microsoft
+implementation in WIMGAPI is included.
+
+ =============================================================================
+ | Compression type || wimlib (v1.7.0) | WIMGAPI (Windows 8.1) |
+ =============================================================================
+ | None [1] || 361,182,560 in 7.6s | 361,183,674 in 11.9s |
+ | XPRESS [2] || 138,992,007 in 11.5s | 140,416,657 in 13.9s |
+ | LZX (quick) [3] || 131,428,113 in 15.2s | N/A |
+ | LZX (normal) [4] || 126,807,853 in 58.9s | 127,259,566 in 55.2s |
+ | LZX (slow) [5] || 126,085,971 in 125s | N/A |
+ | LZMS (non-solid) [6] || 122,082,982 in 59.8s | N/A |
+ | LZMS (solid) [7] || 92,171,126 in 260s | 88,742,356 in 556s |
+ =============================================================================
Notes:
[1] '--compress=none' for wimlib-imagex;
- '/compress none' or no option for ImageX.
+ '/compress:none' for DISM.
[2] '--compress=fast' or '--compress=XPRESS' for wimlib-imagex;
- '/compress fast' or no option for ImageX.
- Compression chunk size is 32768 (the default for XPRESS).
+ '/compress:fast' for DISM.
+ Compression chunk size is 32768 bytes, the default for XPRESS.
- [3] No compression option specified to wimlib-imagex; no known equivalent for
- WIMGAPI (ImageX uses XPRESS compression if no option specified).
- Compression chunk size is 32768 (the default for LZX).
+ [3] No compression option specified to wimlib-imagex;
+ no known equivalent for DISM.
+ Compression chunk size is 32768 bytes, the default for LZX.
[4] '--compress=maximum' or '--compress=LZX' for wimlib-imagex;
- '/compress maximum' for ImageX.
- Compression chunk size is 32768 (the default for LZX).
+ '/compress:maximum' for DISM.
+ Compression chunk size is 32768 bytes, the default for LZX.
[5] '--compress=maximum --compress-slow' for wimlib-imagex;
- no known equivalent for WIMGAPI.
- Compression chunk size is 32768 (the default for LZX).
+ no known equivalent for DISM.
+ Compression chunk size is 32768 bytes, the default for LZX.
[6] '--compress=recovery' or '--compress=LZMS' for wimlib-imagex;
- no known way to create the equivalent with WIMGAPI.
- Compression chunk size is 131072 (the default for LZMS). Note: this
- compression type is not generally recommended due to its limited
- compatibility with the MS implementations.
+ no known equivalent for DISM.
+ Compression chunk size is 131072 bytes, the default for LZMS.
[7] '--compress=recovery --solid' or '--compress=LZMS --solid' for
- wimlib-imagex; WIMCreateFile with WIM_COMPRESSION_LZMS and flag
- 0x20000000 for WIMGAPI. Compression chunk size in packed resources is
- 33554432 for wimlib, 67108864 for WIMGAPI. Note: this compression type
- is not generally recommended due to its limited compatibility with the MS
- implementations. Also, due to the large chunk size, wimlib uses about
- 500MB of memory per thread when compressing in this format.
-
-The above timings were done on Windows 8 (x86) so that side-by-side comparisons
-with the Microsoft implementation would be possible; however, wimlib may have
-even better performance on other operating systems such as Linux. The system
-had 2 CPUs and 2 GiB of memory available. All times were done with the page
-cache warmed, so the times primarily measure the performance of the compression
-algorithms and not the time to read data from disk, which presumably is similar
-in each implementation.
-
-Below are results for compressing the Canterbury corpus using wimlib (v1.6.1),
-WIMGAPI (Windows 8), and some other formats/programs, including the archive size
-only. Note that the Canterbury corpus includes no duplicate files or hard
-links, which WIM handles better than most other formats by storing only distinct
-data streams.
+ wimlib-imagex. Should be '/compress:recovery' for DISM, but it doesn't
+ work; I called WIMGAPI directly instead.
+ Compression chunk size in solid blocks is 67108864 bytes in both cases.
+
+I did the timings on Windows 8.1 running in a virtual machine so that
+side-by-side comparisons with the Microsoft implementation would be possible.
+However, do note that wimlib may have even better performance on other operating
+systems such as Linux. I used the 64-bit builds of both programs.
+
+The compression ratio provided by wimlib is also competitive with commonly used
+archive formats. Below are file sizes that result when the Canterbury corpus is
+compressed with wimlib (v1.7.0), WIMGAPI (Windows 8), and some other
+formats/programs:
=================================================
| Format | Size (bytes) |
| ZIP (Info-ZIP, -9) | 732,297 |
| WIM (wimlib, LZX quick) | 722,196 |
| WIM (WIMGAPI, LZX) | 651,766 |
- | WIM (wimlib, LZX normal) | 639,464 |
- | WIM (wimlib, LZX slow) | 633,144 |
- | WIM (wimlib, LZMS non-solid) | 590,252 |
+ | WIM (wimlib, LZX normal) | 649,204 |
+ | WIM (wimlib, LZX slow) | 639,618 |
+ | WIM (wimlib, LZMS non-solid) | 592,136 |
| tar.bz2 (bzip, default) | 565,008 |
| tar.bz2 (bzip, -9) | 565,008 |
- | WIM (wimlib, LZMS solid) | 534,218 |
- | WIM (wimlib, LZMS solid, slow) | 529,904 |
+ | WIM (wimlib, LZMS solid) | 525,270 |
+ | WIM (wimlib, LZMS solid, slow) | 521,700 |
| WIM (WIMGAPI, LZMS solid) | 521,232 |
| tar.xz (xz, default) | 486,916 |
| tar.xz (xz, -9) | 486,904 |
| 7z (7-zip, -9) | 483,239 |
=================================================
+Note: WIM does even better on directory trees containing duplicate files, which
+the Canterbury corpus doesn't have.
+
NTFS SUPPORT
WIM images may contain data, such as alternate data streams and
git://wimlib.net / wimlib / commitdiff