Backup compression question
I have a Documents directory that is 53.2 MB in size. Using ark, I backed it up to another hard drive as a tar file. The tar file is 53.5 MB. I thought that the file would be smaller in size. What am I missing here? If it becomes larger, I could just do a cp command, and save space! Is it ark that is the problem? Harry G
* Harry G (harrycg@attbi.com) [021231 12:55]:
I have a Documents directory that is 53.2 MB in size. Using ark, I backed it up to another hard drive as a tar file. The tar file is 53.5 MB.
Tar is for creating archives of files, not compression; there's no point in making a tar archive of one file. Use gzip or bzip2 to the compress the file. -- -ckm
Hi, According to the Linux man page on tar, tar has several options for compression. I have used -j. -Z and -z which seem to work well. But I have never used {-use-compress-program=PROG] or [--block-compress] so I can not speak to that. TAR OPTIONS [-j, --bzip2, --bunzip2] [-Z, --compress, --uncompress] [-z, --gzip, --ungzip] [--use-compress-program=PROG] [--block-compress] I hope this helps Abraham Christopher Mahmood wrote:
* Harry G (harrycg@attbi.com) [021231 12:55]:
I have a Documents directory that is 53.2 MB in size. Using ark, I backed it up to another hard drive as a tar file. The tar file is 53.5 MB.
Tar is for creating archives of files, not compression; there's no point in making a tar archive of one file. Use gzip or bzip2 to the compress the file.
-- Abraham Bloom, CISSP | The New Testament offers the basis for modern abrahambloom@comcast.net | computer coding theory, in the form of an X/motif/c/shell/perl | affirmation of the binary number system. Sys V/BSD/Linux/Sco | | But let your communication be Yea, yea; nay, | nay: for whatsoever is more than these cometh | of evil. -- Matthew 5:37
Harry G wrote:
I have a Documents directory that is 53.2 MB in size. Using ark, I backed it up to another hard drive as a tar file. The tar file is 53.5 MB.
I thought that the file would be smaller in size. What am I missing here?
If it becomes larger, I could just do a cp command, and save space! Is it ark that is the problem?
Harry G
from what I recall....tar doesn't have that good of a compression...I think bzip is better from what I recall reading about the specs. I usually use rar...it works on just about any platform and also has very tight compression.
On Tuesday 31 December 2002 12:56 pm, Harry G wrote:
I have a Documents directory that is 53.2 MB in size. Using ark, I backed it up to another hard drive as a tar file. The tar file is 53.5 MB.
I thought that the file would be smaller in size. What am I missing here?
as others have mentioned, "vanilla" tar files are not compressed; under (gnu) linux, tar files with extensions of .tgz or .tar.gz represent tar files that are compressed [after being built] with gzip/gunzip. These will be the most common, though the "B" zip/unzip programs provide more compression
If it becomes larger, I could just do a cp command, and save space! Is it ark that is the problem?
but wait, there's more! What sort of documents are you archiving? If you happen to be archiving "openoffice.org" documents [also known as star office] then using compression may indeed "expand" the files -- OO/So 6 files are already compressed [dump the first part of a file w/more or less and you'll see the "magic" field that indicates compression] decompress the "document" and you'll find it is an XML file (but I digress) Files compressed once don't re-compress very well, and usually expand -- I just have to shake my head when I download a big file and decompress it to find all it contained was another compressed file/archive [like someone compressing a .zip file into a .tar/.tgz file, for instance]
participants (5)
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Abraham Bloom -
Christopher Mahmood -
Harry G -
Oskar Teran -
Tom Emerson