Re: Archiving

Begin <e52449f7-fdf0-4ea0-9d07-d79af7ed53cf@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
On Thu, 17 Jul 2008 14:01:33 -0700 (PDT), J <skyliner306@xxxxxxxxx> wrote:

Two beginner questions about archiving on Unix:

1. How reliable are tar and gzip compared to commercial archiving
products?

tar -- Tape Archiver, method for storing files on a tape, does what it
does pretty well modulo its many versions and file format variations.
Compare star, `bsd tar', pax, cpio, gnu tar, and so on and so forth.
Not all are compatible.

gzip is a stream compression tool like compress and does not do
archiving. Since tar does not do compression, the two are often
combined. See also other such tools like compress (older than gzip) and
bzip2 (newer ~ ~).

Please elaborate: what do _you_ mean with reliability? How do you
expect commercial and non-commercial software to differ?


2. Assuming space is not an issue, is there any benefit in storing
compressed data?

Given that the point of compression is reducing space requirements,
not directly, no.


In other words, would my text, pdf, audio files "keep" any better
being tar'd and gzip'd first?

As noted, tar does not itself provide compression. Any tar that does,
does so by invoking some stream compressor over its output stream.

Both tar and gzip trade complexity for something (combinding files into
one bytestream and compression respectively) which introduces various
risks. The need for specialised tools to extract them again, for one,
and inability to restore the original files from the stream due to
corruption for another. This is more finnicky for compression tools, so
uncompressed tape archives stand a somewhat better chance of recovery
beyond a bad spot (eg. due to media failure).

Then again, if you store your files for 30 years and after 30 years it
turns out you have no programs and/or hardware left to read them....

So you'll need to spell out more clearly what you mean with `keep better'.


--
j p d (at) d s b (dot) t u d e l f t (dot) n l .
This message was originally posted on Usenet in plain text.
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