Re: AW: AW: How to check integrity of database?

On Wed, 2005-10-05 at 15:14 +0200, Markus Karg wrote:
> I don't know the internal structures of FSFS, but what happens if FSFS
> returns buggy data? Is svn verify checking that the data is correct or
> does it trust on FSFS to never return buggy data (i. e. data that
> looks correct but actually is screwed: e. g. the original source line
> would be
>
> "class x"
>
> but FSFS returns
>
> "class y"
>
> because of internal mislinked pages.
>
> Can this happen in FSFS and if it happens, does svn verify detect it?
>
> I think now it's clear what I want to check for?
>

I [arguably] don't know all the details of how it works, but these sort
of checks are definitely a part of what happens. For example, I took
one of my FSFS repositories and munged one of the internal files (I
changed a single byte, just like your example). When verify got to
that revision, I got a nice error:
  ...
  * Verified revision 99.
  svn: Checksum mismatch while reading representation:
     expected: 4ec62b6b4fd5336a67ce148a9b4fabd7
       actual: c200993287dccf718c8ba2bdb5075f25
which told me that it had failed trying to verify revision 100 (the one
I messed with).

So, in summary, I think that 'svnadmin verify' does what you are asking.

>
>
> Mit freundlichem Gruss / With kind regards
> Markus KARG, Staatl. gepr. Inf.
> Entwicklung / R & D
> QUIPSY QUALITY GmbH
>
>
> ______________________________________________________________________
> Von: Gary Thomas [mailto:gary@mlbassoc.com]
> Gesendet: Mi 05.10.2005 14:55
> An: Markus Karg
> Cc: SVN Discussion
> Betreff: Re: AW: How to check integrity of database?
>
>
>
> On Wed, 2005-10-05 at 14:46 +0200, Markus Karg wrote:
> > I just wanted to know whether this *is* a sufficient check, or not.
> > I'm asking this because I have often seen database that worked well,
> > but used broken or misleading links internally. This means, never an
> > error appeared, but the data shown to the user was screwed. So the
> > question is: Does svnadmin verify actually test the FSFS integrity,
> or
> > does it only read each file? If it does the first, I am happy. If it
> > does the last, it will not find misleading links. That's why I asked
> > for a special FSFS tool but not for a SVN tool. So is there a FSFS
> > guru near to answer this?
>
> It does check that every revision can be reconstructed (identical
> to dumping the repository without saving the results). I don't see
> that anything else is necessary.
>
> >
> >
> >
> > Mit freundlichem Gruss / With kind regards
> > Markus KARG, Staatl. gepr. Inf.
> > Entwicklung / R & D
> > QUIPSY QUALITY GmbH
> >
> >
> >
> ______________________________________________________________________
> > Von: Gary Thomas [mailto:gary@mlbassoc.com]
> > Gesendet: Mi 05.10.2005 14:42
> > An: Markus Karg
> > Cc: SVN Discussion
> > Betreff: Re: How to check integrity of database?
> >
> >
> >
> > On Wed, 2005-10-05 at 14:38 +0200, Markus Karg wrote:
> > > Some relational databases (also Microsoft VSS) come with their own
> > > tools to check integrity of the logical database structure (e. g.
> it
> > > might be a page is corrupted etc.). Is there such a tool for FSFS?
> I
> > > mean, can FSFS be broken and how can I detect this as early as
> > > possible so I can restore the latest backup before and major loss
> > > occurs?
> >
> > Is this not sufficient?
> >
> > svnadmin help verify
> > verify: usage: svnadmin verify REPOS_PATH
> >
> > Verifies the data stored in the repository.
> >
> > --
> > ------------------------------------------------------------
> > Gary Thomas | Consulting for the
> > MLB Associates | Embedded world
> > ------------------------------------------------------------
> >
> >
> >
> >
> --
> ------------------------------------------------------------
> Gary Thomas | Consulting for the
> MLB Associates | Embedded world
> ------------------------------------------------------------
>
>
>
>

-- 
------------------------------------------------------------
Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
------------------------------------------------------------
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