Re: [BackupPC-users] restore from a read only file system possible?

On Tue, Oct 11, 2011 at 09:14:33PM +0100, Tim Fletcher wrote:
> On Tue, 2011-10-11 at 19:57 +0000, John Rouillard wrote:
> > On Tue, Oct 11, 2011 at 01:10:30PM +0200, Frank Wolkwitz wrote:
> > > After raid controller failure the pool file system is running in read 
> > > only mode.
> > > Making a file system check would take several days (ext3 fs, 13TB of 16 
> > > TB used) and success is not garanteed.
> > > 
> > > So the question is: Is it possible to run backuppc in a read only 
> > > environment, not to make backups, but to restore files?
> > 
> > Well maybe but why would you. If the filesystem is inconsistent, how
> > do you know that the file you are restoring points to the proper data?
> 
> That's where checksums come in

Well if the pc/system/share/some/random/file is a hard link to the
wrong file because the filesystem metadata is screwed up how would you
detect it? The checksums are in the files right, so the data coule be
correct but it's data for the wrong file.

Also are the checksums verified during restore? I though the checksum
verification was done during backups. Isn't that what the

  $Conf{RsyncCsumCacheVerifyProb} = 0.05;

setting controls? Also we don't know that he is using the rsync backup
method which I think is the only one that does checksums (and only if
checksum caching is enabled) right?

-- 
                                -- rouilj

John Rouillard       System Administrator
Renesys Corporation  603-244-9084 (cell)  603-643-9300 x 111

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