On Wednesday 05 August 2009, liang cao wrote:
> hello
>I have read some documents about amanda.I don't understand that at least one
>full backup within 7days(if I set dumpcycle 7 days).Is it a real full
>backup?
>For example,I have directories (home1,home2,home3,home4,home5,home6,home7)
>and the dumpcycle is 7 days.As the documents said,amanda will perform a full
>dump of 1/7th
> of all file systems each day, and perform incremental dumps on the rest of
>the 6/7th of file systems.
>If the day is first day(monday) of the first week,first day to use
>amanda,does that mean no incremental dumps on the day ?

Only marginally true for a system that is just getting setup.  Once it has 
been running for a while, it will shuffle the backup schedule around so that 
the size of the backups (total size to tape) are more equal on a day to day 
basis.  It will do this by, if there is space on the media, promoting a level 
2 to a level 1, or even a level 0, those dle's that it now knows are smaller 
ones, while not delaying a full level 0 by more than 1 day.  If the media is 
being under-utilized, one can shorten the dumpcycle by one day, which would 
have the effect of making it use 90% of a tape rather than 70% of a tape after 
it has adjusted to the shortened dumpcycle.  But I wouldn't do that without at 
least a months observation & a bit of calculator tapping to see if it will fit 
the media.

I ran with DDS2 tapes for quite a while, and when it worked, the tape filling 
was 95+% every night.  But the service dependability of the DDS2 format 
eventually broke me of that habit, and I have now been running with a vtape 
setup for about 4 years.  Hundreds of times more dependable, random access to 
the backups and now with SATA drives, about 10x faster.

>Suppose that I want to recover all of my data on tuesday of the second
>week,will amanda use the dump image in the first week ?

Amanda has all sorts of those abilities.  Reading the man-pages should show 
you how to work that magic.  It will in effect, use all dump images up to that 
date, recovering the last level 0 before the date set, and all incrementals 
between that level 0 and the preset date/time

>Suppose that home1 is full backed up on monday,but the full back up of home1
>has been destroyed,does that mean the after 6 days' dump images can't be
>used(because they only have the incremental dumps,it's useless if we don't
>have the full dump)?

See above.

>In a word ,I can't understand how to recover the data if amanda use a
>different backup scheduling.

Amanda keeps records, and deletes records.  Basically, if you have an existing 
tape that has not, due to the length of the tapecycle set in amanda.conf and 
it has been running for as long as the tapecycle, then amanda has the records 
and can use them.

Here I am using a 1TB SATA drive as the storage medium, dumpcycle is 4 days, 
and tapecycle is 30.  So at any one time I actually have 7.5 full dumpcycles 
of data on hand I can restore from.  So if I delete something and don't find I 
still need it for 3 weeks, then it is still available and recoverable.

>Could you describe the exact processes of recovering or give me a document ?

That is pretty complex.  I would recommend you pull the tarballs from zmanda's 
site, build it, and study the man pages.                                        
                                                                                
                                                                               

>If the data which is dumping is changed,what will amanda do?

This is what the 'level's of backups are.  A level 0 is a full image.  A level 
1 is everything that has changed since that level 0.  A level 2 is everything 
that changed since the level 1.  And within the limits of the dumpcycle, could 
even goto level 6 for a 7 day dumpcycle.  OTOH, I don't recall seeing it go 
beyond a level 4.

>My mother tongue is not English,wish that you could understand my meaning.
>thank you!

Your English is good.

-- 
Cheers, Gene
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