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I have a server with 8TB data, and a tape with high numbered 400GB tape cartridges. What would be the best solution to backup this server with the least effort ? I think after one full backup, I can make many increments on one 400GB tape. But how can I make the full backup across the tapes (with manual tape change), and how can I restore one file from the full backup and the increments ?

Is there any easy way to do that like disk based tar backup ?

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You know that "tar" stands for "Tape ARchive", right? –  Ignacio Vazquez-Abrams Mar 24 '11 at 18:06
    
Of course. But tar for multiple tapes, generate incremental backups to tapes, search file across multiple tapes, are not my expertise –  Glendyr Mar 24 '11 at 18:08
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You should almost certainly buy a higher capacity tape drive, and tapes, or give up on tapes and go to hard drives. Shuffling that many tapes is almost certainly not something you do not want to rely on. –  Zoredache Mar 24 '11 at 18:49
    
New tape drive is not an option (too expensive), the data not used to change heavily, only 1GB/week. It's not seem too hard work to make a full backup, and daily increments. –  Glendyr Mar 24 '11 at 20:02
    
+1 for backing up to hard disk. Tar (+GPG depending on what you're backing up) to a few big external usb drives, or a cheap NAS box, will be waaaaaaay easier all the way around, both for backup and restore. –  nedm Mar 24 '11 at 20:51
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7 Answers

up vote 6 down vote accepted

Don't try and do it yourself. You should be using a program such as amanda or bacula to manage your backups.

Use amanda when you don't have a tape library.

Use bacula when you have a tape library available.


mini rant follows

Sure, just using dump or tar works and is simple.

How easy is it to restore a certain file from a week ago? A month ago? How do you keep track of what's where? Remember, backups are easy, but restores are the important part.

You can design a method to keep track of what's going on and do all that work yourself. Go ahead! Enjoy the pain when things get complicated. But what you gain from taking the short amount of time out of your schedule to configure amanda (okay, it's more for bacula, but it's more complex. Bigger investment, bigger setup, bigger return) you get back almost immediately. We use it for even single-server backup scenarios as it's so easy to set up and you gain what you spent many times over in the long run.

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With amanda don't you have to have enough spare local storage to perform a full backup which it will then split up and saved to tapes? –  Zoredache Mar 24 '11 at 18:55
    
No, you don't need to stage to disk first. –  MikeyB Mar 25 '11 at 4:38
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I've used all sorts of backups. Certainly Bacula is a reliable way to perform backups, but I think part of the question revolved around security and simplicity. It is harder to find an easier or more reliable means of backing up a file system than to use good old dump. (This presumes that you are using a file system supported by dump. According to tests done over the years, it is certainly better than tar which has few error correcting capabilities, and after an initial level 0 dump you can easily perform incremental backups.

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Sure, just using dump works and is simple. But how easy is it to restore a certain file from a week ago? How do you keep track of what's where? Remember, backups are easy, but restores are the important part. You can design a method to keep track, do all that work yourself. But what you gain from taking the short amount of time out of your schedule to configure amanda (okay, it's more for bacula, but it's more complex) you get back almost immediately. We use it for even single-server backup scenarios as it's so easy to set up and you gain what you spent many times over in the long run. –  MikeyB Mar 25 '11 at 4:43
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I'd certainly recommend full backups over incremental backups - it just saves so much pain!

While you can do it with tar (at least the you can with the Gnu version of tar), I'd recommend using something a bit more robust - I like afio (unlike tar where you put files in an archive then compress the archive, afio compresses the file first then adds it the archive - a much more robust solution - and it will use any program you have available for compression!). It handles multivolume stuff.

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I would suggest to do full initial backup that spans multiple tapes and then do differential backups over 5-7 tapes on daily basis. When size of differential backup grows to fill a full tape take another full backup and start the cycle over. In your case it will be one full backup about once a year. You could use Amanda to set it up.

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#!/bin/bash

INCR_LOG = "/var/log/increment.snar"
DAY_OF_WEEK = $(date +%u)

if [ $DAY_OF_WEEK = 0 ]; then
  rm $INCR_LOG;
fi

tar -cf archive-$DAY_OF_WEEK.tar --listed-incremental=$INCR_LOG /dir/to/be/backed/up

Something similar to that, set it up to run everyday in crontab. Will make a weekly full backup and daily incrementals.

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use 'tar -xf archive.tar /file/in/archive' to extract a single file. –  Zach Dunton Mar 24 '11 at 20:28
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As always with backups, "Best" refers to what you are backing up, why you are backing up (i.e. what your are trying to mitigate through backups), what tools you have, how much data, how often, retention policy, etc.

I do use tar for mine. Amanda and Backula are too big/complicated IMHO for a single machine backup, but it all depends on the things listed above.

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I agree. I check Bacula and Amanda, but there is one server and one tape. Too big. I backup 500MB data files primarily, but there are plenty of them. But many 400GB tapes too. Manuals doesn't cover the problem tar over multiple tapes without tape library. –  Glendyr Mar 24 '11 at 18:28
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Have look in this link has every small details for tap backup

http://www.cyberciti.biz/faq/linux-tape-backup-with-mt-and-tar-command-howto/

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It seems doesn't cover the problem, how backup 8TB on 20 x 400GB tapes. –  Glendyr Mar 24 '11 at 18:32
    
@Glendyr, that link does mention how to use the multi-volume option of GNU tar to create a single tar archive across multiple tapes with manual intervention/swapping if it's the spanning multiple tapes things that you're asking about. See gnu.org/software/tar/manual/html_node/… –  rthomson Mar 25 '11 at 5:30
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