On Sun, Aug 21, 2011 at 07:47:59AM +0200, Thomas Marko wrote:
> Hi,
>
> I have a question regarding dump levels in Amanda. I do backup several DLEs
> with an Amanda server 3.2.1 on a dedicated machine (Ubuntu Natty). On another
> machine (Ubuntu Lucid, Amanda 2.6.1) there is a DLE which approx. 175GB data.
> The first time backup was a level 0 backup with approx. 175 GB (surprise :-).
> Then Amanda made level 1 backup and dumped just changes (some megs, which is
> fine, my bumpsize is 1MB). After that, Amanda made a level 1 with 175 GB
> (WTF?).
>
> Is this as designed? Could one explain to me how Amanda works? I really read
> many things about Amanda on Zmanda website and several boards and I also
> follow this maillinglist for a while, but wether I missed this information or
> I could not find it. I know that Amanda decides by herself when she makes
> level 0 within the dumpcycle and she always ensures that at minimum one is
> available. But why are level >0 dumps sometimes the same size as a level 0?
>
> In my understanding Amanda should backup first a level 0 with 175GB and then
> bump to level 1, as soon as the saved disk-space is more than 1 MB
> (bumpsize). This will dump just a few MBs as the changes on this DLE are
> really small and very rare.
> After that I would expect that Amanda will make level 1 with very small
> amount of data, as there again are practically no changes in the filesystem
> (each level bumpsize will be multiplied with 1,5 in my case (bumpmult)). But
> Amanda makes a level 1 dump again with 175GB!?
> After that Amanda bumped to level 2, and dumped a few MBs (as expected). But
> the next day a level 2 occurred with 175GB. This was done also the next day:
> Level 2 with 175GB.
>
> I always thought, that dumps > level 0 are just incremental. Why is that
> different in Amanda? What I would expect or what I want to achieve is the
> following:
>
> Within 14 days I want to run dumps every day to backup as less as possible
> the full DLE data (level 0) the other days I want to dump just changes, as my
> DLEs change very rare and the changed data is normally really small (I am
> backing up private data not in a company). How can I achieve this with Amanda?
>
> I have about 21 DLEs with sizes between some MBs and 175GB and work with
> 100GB vTapes. I tried to force Amanda to do smaller dumps by setting runtapes
> to 2 or 3, but than Amanda moans that dumps are way too big (of course they
> are, if Amanda makes that large level >0's)...
>
Thomas,
Assuming you are using gnutar for backups I ditto Gene's comment about
checking the archives for similar problems. ISTR that there were some
situations that could cause tar to think the dumps were coming from a
different device. So to tar, a file was deleted and even though it was
the same name, as it was on a "different device", it was a new file.
Typically, if a dump at an incremental level were going to be so large
and so similar to a level 0 dump, amanda would do a new level 0 dump.
Without guessing at its cause I think your "uber-strange" behavior of
not returning to level 0's is being caused by the cycle of 1 day of
normal incrementals at each dump level and the forced remaining at
that level by the default "bumpdays 2".
I suspect that if you set bumpdays to 1 you would see alternating days
of level 0,1,0,1,0,1 ... Still not good, but simpler to analyze and
state the problem;
Why does gnutar think all of your files have changed?
I think gnutar uses a combination of factors to decide if a file has
changed. I'm sure one factor is the file time stamps, notably data
write and inode change times (as shown by ls -l and ls -lc). Might
you have an 'every other day cronjob' that does something with each
file on that DLE?
As noted above, changed devices could affect it also. Might that
DLE reside on an external media such that when you reboot or mount
and unmount the media could assign different device ids?
Jon
--
Jon H. LaBadie [email protected]
JG Computing
12027 Creekbend Drive (703) 787-0884
Reston, VA 20194 (703) 787-0922 (fax)
