> -----Messaggio originale-----
> Da: owner-amanda-users AT amanda DOT org
> [mailto:owner-amanda-users AT amanda DOT org] Per conto di Jon LaBadie
> Inviato: lunedì 12 dicembre 2005 16.15
> A: amanda-users AT amanda DOT org
> Oggetto: Re: Verify backup
>
>
> On Mon, Dec 12, 2005 at 03:18:24PM +0100, Paul Bijnens wrote:
> > Montagni, Giovanni wrote:
> > >I'm wondering if there's a command or a way to check if
> files backed
> > >up
> > >were written to tape cerrectly.
> > >
> > >The amverify command, as explained in the docs, "determines if the
> > >tape
> > >is readable, but does not do any internal consistency
> check on the image."
> >
> > But just before it says: "and pipes the output to a restore program
> > (if
> > available) with an option to create a catalogue of the backup.
> >
> > For gnutar backups, it passes the image through "tar -t",
> producing a
> > table of contents, which would trigger quiet a lot of
> internal errors
> > in the file.
> >
> > >
> > >How can i control if files are written correctly?
> >
> > Doing a test restore from time to time.
So i cannot trust amverify report? This is not a good news...
>
> Giovanni, one thing to consider is that between the time
> amanda backs up a file and the time you attempt to verify the
> accuracy of that backup, many files are likely to have
> changed, been deleted, or added. Unless you are using file
> system snapshots to give you a static file system to back up,
> file by file veri- fication is not very feasible.
>
Can amanda write a sort of checksum (md5 hash?) of the image (entire backup or
single DLE) stored in the holding disk and then compare to the checksum of the
image stored on tape? Or i have to check it manually? Or probably i am saying
stupid and useless things? :-)
> >
> > Also, remember that, even if the backup is perfect, but you
> specified
> > the wrong top level directory in the disklist, the backup is still
> > useless. Some errrors can only be caught by doing a test restore.
> >
> > Specifying the wrong top level directory is easy!!! Having a very
> > large disk, and splitting it up with DLE's like:
> >
> > bigserver.example.com /bigdisk/[a-m]* comp-user-tar
> > bigserver.example.com /bigdisk/[n-z]* comp-user-tar
> >
> > gives you the false impression, that you covered the whole alfabet.
> > But it omits files beginning with a number, with a dot, with an
> > accented character, etc. (Tip: add an entry that is the
> opposite of
> > the previous
> > instead: "/bigdisk/[^a-m]*" is OK.)
>
> If the disk were split into multiple DLEs as your two
> examples above, then this third pattern would capture [n-z]*
> again. Perhaps a third pattern more like
> "/bigdisk/[^a-mn-z]*" would be more appropriate. I include
> separate ranges, [^a-mn-z], rather than a single range
> "[^a-z]" as it is possible in some character sets that the
> two are different (eg. an accented "m" collates higher than
> "m" but lower than "n").
>
> Another way of doing this, not better - just different, is to
> also backup "/bigdisk" entirely with a separate DLE with a
> unique exclude list to omit the things backed up by the other DLEs.
Yes, i've used the exclude list to avoid possible errors caused by "bad"
patterns.
>
> --
> Jon H. LaBadie jon AT jgcomp DOT com
> JG Computing
> 4455 Province Line Road (609) 252-0159
> Princeton, NJ 08540-4322 (609) 683-7220 (fax)
>
Thanks a lot for your help.
Giovanni
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