Re: Good backup software for Linux
On Tue, 21 Jun 2005 04:17:14 -0300
Rogério Brito <rbrito@ime.usp.br> wrote:
>
> All this backup talk got me thinking: what do you guys recommend for
> backing up workstations with CDs/DVDs for a luser, especially when backing
> up large amounts of data (say, movie and music files) that may not fit into
> one CD/DVD?
You might check this posting[1] on Mandrake expert advocating highly
redundant rar files for the backups. There is a fairly high redundancy
factor that limits errors in the media built in. However, it eats a lot
of CPU to do this well. I've only done limited testing.
[1]
lxaphir@yahoo.com writes:
My suggestion is to use rar. With rar, you can do multivolume archives,
fully compressed, into whatever size you need. I picked a size number
(exactly 36700000 bytes) that would allow me to exactly fill up 700 meg
CD's with little or no slack space left over. There is about 2 meg or so
slack space left over after you put 20 volumes on the CD. You could
just as easily pick a size that would fit exactly to the 4.7 gig size of
a DVD.
Rar also allows you to put "recovery data" in with the archives. These
contain data that can be used to reconstruct a damaged multivolume
archive section. So if something happens to your backup media and
archive volume number 365 happens to be damaged or incomplete, the
recovery volumes (across ALL of the volumes) use their information to
reconstruct that particular volume.
The rar command line I use to archive:
rar a -mdG -r -rr -ol -cl -av- -m5 -v36700000b archive_name
source_files
"a" is a rar "command" and instructs it to create an archive.
-mdG increases the table of contents to max for large numbers of files.
-r instructs rar to be recursive, and descend into subdirectories.
-rr instructs rar to put recovery information in every single archive.
-ol Important. Tells rar to save symbolic links as a file rather than
to follow them.
-cl possibly not needed, but I use it to archive windows partitions;
converts all filenames to lower case. Use judiciously and as needed.
-av- disables volume authentication, which is not available in the free
version of rar anyhow. Omitting this may cause non-critical errors
whenever you access the archives.
-m5 Maximum compression. Unbeatable by any other compression utility in
Linux. Adjust downward if you want faster archiving. Maximum
compression gives you the absolute most data per CD, but it takes alot
of time to create; you may want to sacrifice compression for speed.
Extraction from archives does not seem to be affected by the initial
compression level.
One reason I like multivolume archives, if you don't already know this,
is because of recovery information as well as "risk distribution". Big
files that take up a whole CD are a "bad thing"(tm). You lose the file,
you lose the whole archive. It's much better to split the whole storage
up into recoverable handleable pieces. That way if you lose a piece,
you don't lose the whole thing. Large CD-sized archives are a disaster
waiting to happen. One bad spot on the CD and your data is toast.
Not so with multivolume archives. You lose one archive, you still have
a prayer of recovering the lost piece. The more mulitvolumes you have,
the more the risk is distributed. 20 archives per cd is a number I
chose, however the number of archives per cd could be 30 or 40, if you
greatly value your data. The risk of loss is distributed more as you
increase the number of archives.
With tar, you cannot do multivolume archives unless you are writing to
removable media that can be changed out. That normally doesn't happen
these days for the normal user. I write to free space on the hard drive
first, then burn the result to CD.
Also, with tar or gzip, you can forget recovery capabilities. Not
happening. With rar the compression is superior, multivolume archiving
is possible, recovery information per volume is possible, and if your cd
gets damaged you still have the chance of reconstructing volumes.
Example archive cd listing:
[elx@tamriel elx]$ ll /mnt/cdrom2
total 711500
-r-xr-xr-x 1 root root 36700000 Jan 18 10:24 bg2.part001.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:26 bg2.part002.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:28 bg2.part003.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:30 bg2.part004.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:32 bg2.part005.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:34 bg2.part006.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:36 bg2.part007.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:37 bg2.part008.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:40 bg2.part009.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:42 bg2.part010.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:44 bg2.part011.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:46 bg2.part012.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:49 bg2.part013.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:50 bg2.part014.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:53 bg2.part015.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:55 bg2.part016.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:57 bg2.part017.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 10:59 bg2.part018.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 11:01 bg2.part019.rar*
-r-xr-xr-x 1 root root 36700000 Jan 18 11:03 bg2.part020.rar*
[elx@tamriel elx]$
By using the size value above (with gcombust) I can create exactly 20
volumes that fit perfectly in the "official" space that a 700 meg cd can
hold. Normally I get rar to do a test on the archives after they are
created (before they are burned to cd) and then redirect that output to
a file, which is then put on either the first or the last cd.
rar t bg2.part001.rar > manifest.txt
You can pick up rar from one of the mandrake mirrors, it doesn't come
with the distro.
ftp://ftp.ibiblio.org/pub/packages/rpmhelp/9.2/RPMS/rar-3.1.1-1rph.i386.rpm
If you are running MDK10 or something like that you can get the src and
do an rpm --rebuild on the source package to get a binary rpm for your
distro version:
ftp://ftp.ibiblio.org/pub/packages/rpmhelp/rar-3.1.1-1rph.src.rpm
You would do "rpm --rebuild rar-3.1.1-1rph.src.rpm"
Note -- I have tried other burn software other than Gcombust, and some
of the software I tried could not fit the same amount of information on
the CD's as Gcombust.
LX
> Thanks, Rogério.
--
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David E. Fox Thanks for letting me
dfox@tsoft.com change magnetic patterns
dfox@m206-157.dsl.tsoft.com on your hard disk.
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