subversion fud...and rcs old timers..

["Lindsay, Phil" <pl...@tickets.com>]

We are in the midst of conversion from clear case to subversion.  
Apparently someone in-house built a version of subversion on fedora 1 
(probably incorrectly?) and had a issue with a wedged/locked db file.  This 
raised concerned form rcs folk about the security of source code 
should a db file become corrupted, etc...
 
Folk read Ben's fud note, but there is still some fear, if a db file is 
partially damaged is it recoverable sans backup?  Have there been any 
issues between subversion versions and db structure? Looking for any 
info that can help dispel the fear in some old time rcs folk (yes, 
they used to hack rcs files and are looking for analog to vi 
+ rcs files).
  
Thanks for your time and any info.

Cheers,
-phil (phil "at" lindsay.net)
"Don't confuse my lack of interest as stupidity."


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Re: subversion fud...and rcs old timers..

[Michael W Thelen <th...@cs.utah.edu>]

* kfogel@collab.net <kf...@collab.net> [2004-07-02 13:34]:
> And they're right -- Subversion's repository is less hand-hackable
> than an RCS file tree.  Although Subversion's new FSFS back end is
> probably more hand-hackable than its BDB back end, neither is as
> hand-hackable as plain RCS files.
> 
> I don't know if this helps you make your case or not.  Good luck!

This probably doesn't help the case with the RCS old-timers, but I
actually feel that this trade-off is a drawback of RCS and a strength of
Subversion.  It's easy to screw things up when hacking RCS files (and
maybe not even realize it).  But the Subversion/BDB recovery tools
generally take care of any problems easily and automatically.  I don't
want the responsibility or pain of mucking with the guts of my version
control system to fix a problem when one occurs. :-)

-- Mike

-- 
Michael W. Thelen
I happen to feel that the degree of a person's intelligence is directly
reflected by the number of conflicting attitudes she can bring to bear on the
same topic.     -- Lisa Alther, "Kinflicks", 1975

Re: subversion fud...and rcs old timers..

[kf...@collab.net]

"Lindsay, Phil" <pl...@tickets.com> writes:
> Folk read Ben's fud note, but there is still some fear, if a db file is 
> partially damaged is it recoverable sans backup?

In SVN, as with RCS files or any other storage mechanism, if the
storage is damaged severely and there is no backup, it is possible
that data will be permanently lost.

In SVN, as with RCS files or almost any other storage mechanism, if
the storage is damaged in a non-severe way and there is no backup, you
might still be possible to recover your data, but there are no
guarantees.

When a SVN repository is "wedged" and needs recovery (due to being
accessed with incorrect permissions or whatever), there is no data
loss.  Your data is still in there, and when the repository is
recovered you will be able to access it again.

None of this addresses the concern of the RCS old-timers, of course.
What they're really saying is "If something goes wrong, I feel I can
hand-hack RCS files and recover a lot of the data, but I don't feel
that way about Subversion."

And they're right -- Subversion's repository is less hand-hackable
than an RCS file tree.  Although Subversion's new FSFS back end is
probably more hand-hackable than its BDB back end, neither is as
hand-hackable as plain RCS files.

I don't know if this helps you make your case or not.  Good luck!

-Karl

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Re: subversion fud...and rcs old timers..

[Max Bowsher <ma...@ukf.net>]

Brian Mathis wrote:
> Max Bowsher wrote:
>
>> Lindsay, Phil wrote:
>>
>>
>>> We are in the midst of conversion from clear case to subversion.
>>> Apparently someone in-house built a version of subversion on fedora 1
>>> (probably incorrectly?) and had a issue with a wedged/locked db file.  This
>>> raised concerned form rcs folk about the security of source code
>>> should a db file become corrupted, etc...
>>>
>>>
>>
>> A wedged db hasn't lost any data.
>>
>>
>>
>>> Folk read Ben's fud note, but there is still some fear, if a db file is
>>> partially damaged is it recoverable sans backup?
>>>
>>>
>>
>> Depends on the extent and type of damage.
>>
>>
>>
>>> Have there been any
>>> issues between subversion versions and db structure?
>>>
>>>
>>
>> I don't understand the question.
>>
>>
>>
>>> Looking for any
>>> info that can help dispel the fear in some old time rcs folk (yes,
>>> they used to hack rcs files and are looking for analog to vi
>>> + rcs files).
>>>
>>>
>>
>> Well, If it really comes to that, the equivalent to vi is a scripting
>> language with berkeley DB bindings.
>>
>> But, seriously, all you have to do is implement a sensible backup regime.
>>
>> You can even use post-commit hooks to save incremental dumps of new
>> revisions as they are committed, until the next actual backup.
>>
>> Max.
>>
>>
>>
>
> You must admit, it's a little hard to sell something when it comes with
> the stipulation "You really, REALLY need to have good backups because
> something can go wrong, and probably will go wrong".

That wasn't what I intended to imply. Let me clarify:

All have to do, *to allay the last lingering doubts in your team*, is implement a sensible backup regime.

> Personally I think the DB backend is much more touchy than even the
> backend files for other things like postgresql - i think mostly due to
> the multiple access methods.  If you stick to one and only one access
> method, either through svnserve or apache, the problems are reduced.
>
> Having said that, 1.1 will give you the option to use a file system
> backend, which I'm betting will be much more robust.

We've had _occasional_ reports of corruptions, its true. Only a fraction of those have been truly severe. Also, bear in mind that
you are likely to find out about a corruption, whereas with cvs, it's likely to go undetected.

Also, bear in mind that fsfs hasn't been released yet, so the vast majority of successful subversion users are using the bdb
backend.

Max.



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Re: subversion fud...and rcs old timers..

[Brian Mathis <bm...@directedge.com>]

Max Bowsher wrote:

>Lindsay, Phil wrote:
>  
>
>>We are in the midst of conversion from clear case to subversion.
>>Apparently someone in-house built a version of subversion on fedora 1
>>(probably incorrectly?) and had a issue with a wedged/locked db file.  This
>>raised concerned form rcs folk about the security of source code
>>should a db file become corrupted, etc...
>>    
>>
>
>A wedged db hasn't lost any data.
>
>  
>
>>Folk read Ben's fud note, but there is still some fear, if a db file is
>>partially damaged is it recoverable sans backup?
>>    
>>
>
>Depends on the extent and type of damage.
>
>  
>
>>Have there been any
>>issues between subversion versions and db structure?
>>    
>>
>
>I don't understand the question.
>
>  
>
>>Looking for any
>>info that can help dispel the fear in some old time rcs folk (yes,
>>they used to hack rcs files and are looking for analog to vi
>>+ rcs files).
>>    
>>
>
>Well, If it really comes to that, the equivalent to vi is a scripting language with berkeley DB bindings.
>
>But, seriously, all you have to do is implement a sensible backup regime.
>
>You can even use post-commit hooks to save incremental dumps of new revisions as they are committed, until the next actual backup.
>
>Max.
>
>  
>

You must admit, it's a little hard to sell something when it comes with 
the stipulation "You really, REALLY need to have good backups because 
something can go wrong, and probably will go wrong".

Personally I think the DB backend is much more touchy than even the 
backend files for other things like postgresql - i think mostly due to 
the multiple access methods.  If you stick to one and only one access 
method, either through svnserve or apache, the problems are reduced.

Having said that, 1.1 will give you the option to use a file system 
backend, which I'm betting will be much more robust.

-- 
Brian Mathis
http://directedge.com/b/

Re: subversion fud...and rcs old timers..

[Max Bowsher <ma...@ukf.net>]

Lindsay, Phil wrote:
> We are in the midst of conversion from clear case to subversion.
> Apparently someone in-house built a version of subversion on fedora 1
> (probably incorrectly?) and had a issue with a wedged/locked db file.  This
> raised concerned form rcs folk about the security of source code
> should a db file become corrupted, etc...

A wedged db hasn't lost any data.

> Folk read Ben's fud note, but there is still some fear, if a db file is
> partially damaged is it recoverable sans backup?

Depends on the extent and type of damage.

> Have there been any
> issues between subversion versions and db structure?

I don't understand the question.

> Looking for any
> info that can help dispel the fear in some old time rcs folk (yes,
> they used to hack rcs files and are looking for analog to vi
> + rcs files).

Well, If it really comes to that, the equivalent to vi is a scripting language with berkeley DB bindings.

But, seriously, all you have to do is implement a sensible backup regime.

You can even use post-commit hooks to save incremental dumps of new revisions as they are committed, until the next actual backup.

Max.



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Re: subversion fud...and rcs old timers..

[Tobias Ringström <to...@ringstrom.mine.nu>]

Lindsay, Phil wrote:

>We are in the midst of conversion from clear case to subversion.  
>Apparently someone in-house built a version of subversion on fedora 1 
>(probably incorrectly?) and had a issue with a wedged/locked db file.  This 
>raised concerned form rcs folk about the security of source code 
>should a db file become corrupted, etc...
>  
>
Also note that FC1 ships whith Berkeley DB 4.1 which is know to have 
severe issues. Use Berkeley BDB 4.2 if at all possible.

/Tobias


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