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Re: Frequent database corruption

From: Michel Jouvin <jouvin_at_lal.in2p3.fr>
Date: 2005-02-20 11:53:24 CET

--On samedi 19 février 2005 21:12 +0100 Bastian Blank
<bastian+dev=subversion.tigris.org@waldi.eu.org> wrote:

> On Sat, Feb 19, 2005 at 08:06:23PM +0100, Michel Jouvin wrote:
>> > Which cluster filesystem?
>> Tru64/TruCluster Cluster File System. I am not sure about Florian
>> question : the file system (including locks) has the whole semantic of
>> a local file system but that I am not sure about system mutexes. In
>> fact it is possible to create shared memory between cluster nodes but
>> it has to be done explicitly.
>>
>> Anyway, as I explained below, we now run a configuration where we only
>> have one Apache server handling subversion request and I have httpd
>> logs to prove that. I understand that there is may be something wrong
>> in our configuration if we run several concurrent Apachae instances on
>> several nodes accessing the same repositories. But the database
>> corruption we have now are not in this configuration and even not
>> related to commit or other repository modification.
>
> You have to uses fsfs. Berkeley DB shared memory needs shared mapping
> where updates show up in any other mapping. This behavior is not
> required by POSIX and is not possible to do with cluster fs without
> large overhead.
>
> Bastian

As I said, it could (may be) explain the problem we had when running to
instances. But this is NO LONGER the case.

It's not clear for me what you call shared mapping. If you are talking
about mmap(), it is synchronized cluster wide and this should not be the
problem (for example we have an IMAP server relying on MMAP and we never
experienced any corruption in our cluster config). But I suggest to
concentrate on corruption that occurs in the single Apache instance
configuration during GET operations.

Michel

>
> --
> I'm a soldier, not a diplomat. I can only tell the truth.
> -- Kirk, "Errand of Mercy", stardate 3198.9
>
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Received on Sun Feb 20 11:54:25 2005

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