On 2006-05-10 06:42, Olivier Nicole wrote:

Hi,

Correct me if I am wrong. It seems that when a DLE is set to
incremental backup, Amanda will try to get the size using various

How did you specify "incremental backup"?
There are several methods which have an influence:

  skip-full yes      # when planner scheduled a lvl 0 skip it
  strategy nofull    # only level 1 during planning/estimate
  strategy incronly  # similar to skip-full but allows full
                     # dumps with "amadmin force"

The man page also says something about bugs, but I believe those
bugs are already solved a long time ago, but the docs got not updated,
I guess.

level 0.  I also never saw an "unforced full backup" in this config,
but it could be that the period between force is too small for the bug
to happen.

My archive run, which does only level 0 dumps, has the parameter
"strategy noinc", which avoids doing any estimates (or dumps) for
level 1 or higher.  (Save a lot of time and energy.)

Note the the "strategy" parameter works during estimate, while the
other parameters are older, and achieve something similar but a little
different.

Because of the history of these commands, the naming and orthogonal
features of the options are not well choosen.

methods:

- full backup size
- same incremental level as the last one size
- next incremental level size

I see in /tmp/amanda/sendsize... the following lines:

sendsize[78984]: time 27.295: getting size via gnutar for /home/fidji level 0
sendsize[78984]: time 36.611: getting size via gnutar for /home/fidji level 3
sendsize[78984]: time 38.428: getting size via gnutar for /home/fidji level 4

and it happens that the last incremental backup for /home/fidji was
level 3.

Then Amanda would choose what level to use (0, 3 or 4).

I guess that from the above lines you have "skip-full" and not
"strategy incronly".

Do I understand well?

My problem is the following. I need to backup a Zope
installation. Zope keeps all the data in one single BIG file (it
quickly grows GBs). Amanda cannot do proper backup on the fly so I
need to either:

- stop zope during the backup. Easy using a gnutar wrapper, but that
  would put my web site away for some time.

- use a tool provided by zope to make a safe copy of that big data
  file and backup that copy.

That tool allows incremental copies. How nice, I could match the

  full copy with Amanda full backup and incremental copies with Amanda
  incremental copies... But to get the size right, I need to make the
  copy at the size estimate stage, not at the dump stage. And the size
  estimate of Amanda always proceed to do a full estimate, so I would
  end up anyway using Zope tool to do a full copy.

  If I do the copy at dump type only, the size estimate will be all
  wrong (eventually by a large amount). How much can that affect
  Amanda?

If I understand your problem is that doing an estimate for lvl 0, N, N+1
takes too long, especially the lvl 0.

If your tape drive is large enough, meaning, you can live with less
accurate estimates, you could switch to "estimate server", instead of
the default "estimate client".

In "estimate server" the estimates are based on statistics of the
previous runs.  If the differences between runs of the same level are
not big, then those estimates will be good enough.
And you get a big speedup during estimate.  And the wrapper need only
make the level 0 zope dump, when Amanda has scheduled it.


--
Paul Bijnens, xplanation Technology Services        Tel  +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
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