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From Geoff Field <Geoff_Fi...@aapl.com.au>
Subject RE: Trying to restore a corrupted repo
Date Thu, 26 Feb 2015 02:41:01 GMT
[snip]
> First step is to *write lock* the old repository, to avoid 
> accumulating history on broken history.

Absolutely - and make sure the lock stays locked forever more.

> You will be *breaking history* due to the corrupted repo. You 
> should ideally create a new repo to do the repairs in, 
> explain the situation,and tell your user community to set 
> aside their working copies and make clean checkouts when 
> you're done. The old repo should be locked, and the new repo 
> should have a new name to avoid any confusion.

What I've done in the past is to:
a) Write-lock the old repository;
b) Create and populate a new repository by whatever means are required;
c) Ensure nobody is trying to access either repository for the next few steps (pause Apache,
or whatever);
d) Re-name the OLD repository to reflect its broken/BDB/whatever status;
e) Rename the NEW repository to the old name; and, finally:
f) Re-enable access to the repositories.

I even created a batch file to do this when we upgraded SVN recently and could no longer access
the BDB repositories.

> This is one of the difficulties with the absolute central 
> repository approach of Subversion and its spiritual ancestor, 
> CVS. If anything happens to the central repository, you have 
> to re-establish the effectively server/client relationship 
> correctly or be at risk of corrupting your history, *again*.

This is why your servers should have an effective backup and restoration system.  Ours uses
a SAN with off-site backup.  Then, if we catch the corruption early enough we've only lost
a day's history.

> It can happen with more distributed systems as well, it's 
> just more likely when one particular repository is considered 
> canonical in your particular workflow. If the history is 
> replaced or corrupted behind your back, you can be in real trouble.

I think this is true of any single-site storage system - electronic or otherwise.  If there's
a single point of failure, and you rely on the information/items, there's potential for (business)
disaster.

Regards,

Geoff

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