Why is *.tar.gz still much more common than *.tar.xz?

Why is *.tar.gz still much more common than *.tar.xz?

Whenever I see some source packages or binaries which are compressed with GZip I wonder if there are still reasons to favor gz over xz (excluding time travel to 2000), the savings of the LZMA compression algorithm are substantial and decompressions isn't magnitudes worse than gzip.

Answer by SF. for Why is *.tar.gz still much more common than *.tar.xz?

"Lowest Common Denominator". The extra space saved is rarely worth the interoperability. Most embedded Linux systems have gzip, but not xz. Many old system as well. Gnu Tar which is the industry standard supports flags -z to process through gzip, and -j to process through bzip2, but some old systems don't support the -J flag for xz, meaning it requires 2-step operation (and a lot of extra diskspace for uncompressed .tar unless you use the syntax of |tar xf - - which many people don't know about. Also, uncompressing the full filesystem of some 10MB from tar.gz on embedded ARM takes some 2 minutes and isn't really a problem. No clue about xz but bzip2 takes around 10-15 minutes. Definitely not worth the bandwidth saved.

Anyway, the current "modern alternative" where you sacrifice CPU power in favor of disk space (...which is still rarely a welcome trade - bandwidth and diskspace are cheap, and people hate when systems grind to a halt due to some updates running in background) - is bzip2.

Answer by woliveirajr for Why is *.tar.gz still much more common than *.tar.xz?

For the same reason people in Windows (r) use zip files instead of 7zip, and some still use rar instead of other formats... Or mp3 is used in music, instead of aac+, and so on.

Each format has it's benefits and people use to stick to a solution they learned when began using a computer. Add this to backward compatibility and fast bandwidth + GB or TB of space in hard drives, and the benefits of a greater compression won't be that relevant.

Answer by wujj123456 for Why is *.tar.gz still much more common than *.tar.xz?

Honestly, I just get to know .xz format from a training material. So I just used its git repo to do a test. The git is git://git.free-electrons.com/training-materials.git, and I also compiled the three training slides. The total directory size is 91M, with a mixture of text and binary data.

Here is my quick result. Maybe people still favor tar.gz simply because it's much faster to compress? I personally even use plain tar when there aren't many benefits to be gained in compression.

[02:49:32]wujj@WuJJ-PC-Linux /tmp $ time tar czf test.tgz training-materials/    real    0m3.371s  user    0m3.208s  sys     0m0.128s  [02:49:46]wujj@WuJJ-PC-Linux /tmp $ time tar cJf test.txz training-materials/    real    0m34.557s  user    0m33.930s  sys     0m0.372s  [02:50:31]wujj@WuJJ-PC-Linux /tmp $ time tar cf test.tar training-materials/    real    0m0.117s  user    0m0.020s  sys     0m0.092s  [02:51:03]wujj@WuJJ-PC-Linux /tmp $ ll test*  -rw-rw-r-- 1 wujj wujj 91944960 2012-07-09 02:51 test.tar  -rw-rw-r-- 1 wujj wujj 69042586 2012-07-09 02:49 test.tgz  -rw-rw-r-- 1 wujj wujj 60609224 2012-07-09 02:50 test.txz  [02:56:03]wujj@WuJJ-PC-Linux /tmp $ time tar xzf test.tgz    real    0m0.719s  user    0m0.536s  sys     0m0.144s  [02:56:24]wujj@WuJJ-PC-Linux /tmp $ time tar xf test.tar    real    0m0.189s  user    0m0.004s  sys     0m0.108s  [02:56:33]wujj@WuJJ-PC-Linux /tmp $ time tar xJf test.txz    real    0m3.116s  user    0m2.612s  sys     0m0.184s  

Answer by Jody Lee Bruchon for Why is *.tar.gz still much more common than *.tar.xz?

The ultimate answer is accessibility, with a secondary answer of purpose. Reasons why XZ is not necessarily as suitable as Gzip:

• Embedded and legacy systems are far more likely to lack sufficient available memory to decompress LZMA/LZMA2 archives such as XZ. As an example, if XZ can shave 400 KiB (vs. Gzip) off of a package destined for an OpenWrt router, what good is the minor space savings if the router has 16 MiB of RAM? A similar situation appears with very old computer systems. One might scoff at the thought of downloading and compiling the latest version of Bash on an ancient SparcStation LX with 32MB of RAM, but it happens.

• Such systems usually have slow processors, and decompression time increases can be very high. Three seconds extra to decompress on your Core i5 can be severely long on a 200 MHz ARM core or a 50 MHz microSPARC. Gzip compression is extremely fast on such processors when compared to all better compression methods such as XZ or even Bzip2.

• Gzip is pretty much universally supported by every UNIX-like system (and nearly every non-UNIX-like system too) created in the past two decades. XZ availability is far more limited. Compression is useless without the ability to decompress it.

• Higher compression takes a lot of time. If compression time is more important than compression ratio, Gzip beats XZ. Honestly, lzop is much faster than Gzip and still compresses okay, so applications that need the fastest compression possible and don't require Gzip's ubiquity should look at that instead. I routinely shuffle folders quickly across a trusted LAN connection with commands such as "tar -c * | lzop -1 | socat -u - tcp-connect:192.168.0.101:4444" and Gzip could be used similarly over a much slower link (i.e. doing the same thing I just described through an SSH tunnel over the Internet).

Now, on the flip side, there are situations where XZ compression is vastly superior:

• Sending data over slow links. The Linux 3.7 kernel source code is 34 MiB smaller in XZ format than in Gzip format. If you have a super fast connection, choosing XZ could mean saving one minute of download time; on a cheap DSL connection or a 3G cellular connection, it could shave an hour or more off the download time.

• Shrinking backup archives. Compressing the source code for Apache's httpd-2.4.2 with "gzip-9" vs. "xz -9e" yields an XZ archive that is 62.7% the size of the Gzip archive. If the same compressibility exists in a data set you currently store as 100 GiB worth of .tar.gz archives, converting to .tar.xz archives would cut a whopping 37.3 GiB off of the backup set. Copying this entire backup data set to a USB 2.0 hard drive (maxing out around 30 MiB/sec transfers) as Gzipped data would take 55 minutes, but XZ compression would make the backup take 20 minutes less. Assuming you'll be working with these backups on a modern desktop system with plenty of CPU power and the one-time-only compression speed isn't a serious problem, using XZ compression generally makes more sense. Why shuffle around extra data if you don't need to?

• Distributing large amounts of data that might be highly compressible. As previously mentioned, Linux 3.7 source code is 67 MiB for .tar.xz and 101 MiB for .tar.gz; the uncompressed source code is about 542 MiB and is almost entirely text. Source code (and text in general) is typically highly compressible because of the amount of redundancy in the contents, but compressors like Gzip that operate with a much smaller dictionary don't get to take advantage of redundancy that goes beyond their dictionary size.

Ultimately, it all falls back to a four-way tradeoff: compressed size, compression/decompression speed, copying/transmission speed (reading the data from disk/network), and availability of the compressor/decompressor. The selection is highly dependent on the question "what are you planning to do with this data?"

Also check out this related post from which I learned some of the things I repeat here.

Answer by Student for Why is *.tar.gz still much more common than *.tar.xz?

I did my own benchmark on 1.1GB Linux installation vmdk image:

rar    =260MB   comp= 85s   decomp= 5s  7z(p7z)=269MB   comp= 98s   decomp=15s  tar.xz =288MB   comp=400s   decomp=30s  tar.bz2=382MB   comp= 91s   decomp=70s  tar.gz =421MB   comp=181s   decomp= 5s  

all compression levels on max, CPU Intel I7 3740QM, Memory 32GB 1600, source and destination on RAM disk

I Generally use rar or 7z for archiving normal files like documents.
and for archiving system files I use .tar.gz or .tar.xz by file-roller or tar with -z or -J options along with --preserve to compress natively with tar and preserve permissions (also alternatively .tar.7z or .tar.rar can be used)

update: as tar only preserve normal permissions and not ACLs anyway, also plain .7z plus backup and restoring permissions and ACLs manually via getfacl and sefacl can be used which seems to be best option for both file archiving or system files backup because it will full preserve permissions and ACLs, has checksum, integrity test and encryption capability, only downside is that p7zip is not available everywhere

Answer by Ondrej Bozek for Why is *.tar.gz still much more common than *.tar.xz?

Also one important point for gzip is that it's interoperable with rsync/zsync. This could be huge benefit regarding bandwidth in cases. LZMA/bzip2/xz doesn't support rsync and probably won't support it anytime soon.
One of characteristics of LZMA is that it uses quiet large window. To make it rsync/zsync friendly we would probably need to reduce this window which would degrade it's compression performance.

Answer by jgmjgm for Why is *.tar.gz still much more common than *.tar.xz?

gz is supported everywhere and good for portability.

xz is newer and now as widely or well supported. It is more complex than gzip with more compression options.

This is not the only reason people might not always use xz. xz can take a very long time to compress, not a trivial amount of time so even if it can produce superior results it might not always be chosen. Another weakness is that it can use a lot of memory, especially for compression. The more you want to compress an item by the longer it takes and this is exponential with diminishing returns.

However, at compression level 1 for large binary items in my experience xz can often produce much smaller results in less time than zlib at level 9. This can sometimes be a very significant difference, in the same time as zlib, xz can make a file that is half the size of zlib's file.

bzip2 is in a similar situation, however xz has far superior advantages and a strong window where it performs significantly better all round.

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