helpstoreBackup - Support: sr #108316, lock file / multiple instances

 
 

sr #108316: lock file / multiple instances

Submitter:  None
Submitted:  Sat 08 Jun 2013 12:23:16 AM UTC
 
Category:  None Priority:  5 - Normal
Severity:  3 - Normal Status:  Done
Privacy:  Public Assigned to:  None
Originator Email:  -email is unavailable- Open/Closed:  Open
Operating System:  GNU/Linux
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Sat 08 Jun 2013 10:47:40 AM UTC, comment #2: 

Hi Heiz-Josef,

thanks for the thorough explenation. Each aspect has been covered.

Regarding a further question to the "redundancy problem" I open a seperate sr, so we don't mix topics.

I think this one could be closed.

Thanks !!!

lopiuh

Anonymous
Sat 08 Jun 2013 10:12:34 AM UTC, comment #1: 

Hi,

first of all - that's no problem. You should start both storeBackup.pl's directly in parallel, because then filesystem caching will be perfect and the two backups will take about the same time than one backup. (This is not true if you have really lots of new files to compress and if you have slow cpus.)

In detail:

1. It's a very bad idea to run the_same_backup into the same backupDir multiple times. The result would be not hard linked new files in each backup with no additional advantage.

2. Say you run two different backups into the same backupDir at the same time (different series). If these two backups have no identical files, the result will be the same as running one after the other. In this case, you should set option otherBackupSeries so storeBackup.pl does not waste time reading the md5 sums of the other backup.

3. You run two different backups into the same backupDir at the same time (different series) but have identical files in the backup. This might happen if two people with laptops (and shared files) make independent backups. In this case, the identical new (!) files will not be hard linked. However, starting with the next backup, each of these two different series will hard link against the_same inode in the backup (backupDir). So after some time, the "lonely" hardlink will be removed by deletion of old backups.
If the backups were run sequentially, the new identical files from the different series will be hard linked normally (as long as you do not define something different with option otherBackupSeries).

Also a long answer ;-)

Does it answer your question?

Regards, Heinz-Josef

Heinz-Josef Claes <hjclaes>
Project Administrator
Sat 08 Jun 2013 12:23:16 AM UTC, original submission:  

Hi,

in the manual it is said "running it [storebackup} multiple times (which is a very bad idea)"

is it performance wise a bad idea or are there serious problems which can arise?

Why I ask: I have a cron job doing my main backup in the night. I don't use replication feature. If I run an independant storebackup, say in order to feed an external disk ... would it be a bad idea (corruption) to risk having an extraordinary storebackup running (with its own independant lockfile) and the cron job kicks in and trying to do its backup in parallel?

Thanks

lopiuh

Anonymous

 

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