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Date: Sun, 30 Oct 2011 11:59:47 +0100
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From: Dan Gudmundsson <dan...@gmail.com>
To: Jon Watte <jwa...@gmail.com>
Cc: erlang-questi...@erlang.org
Subject: Re: [erlang-questions] mnesia sync_transactions not fsynced?
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As far as mnesia is concerned it is logged to disc. It have left
mnesia call chain and it's nothing
more mnesia can do, except sync the disk.
Which is a performance penalty that is not acceptable per transaction.

I have been reminded why the disc_log cache was implemented, when you
push transactions
in a short loop, you are pushing more transaction then what can be
pushed to disc.
So that everything was stuck in disc_logs message queue.
The way to improve that was to write larger chunks to the disc.
So removing the timeout in disc_log will probably not change the
situation only that message
will be stuck on message queue instead. It will still not be written
to the disc fast enough.

/Dan

On Sun, Oct 30, 2011 at 2:24 AM, Jon Watte <jwa...@gmail.com> wrote:
>
>
> On Fri, Oct 28, 2011 at 12:18 AM, Dan Gudmundsson <dan...@gmail.com> wrote:
>>
>> Disk log cashes writes as well so you can loose many writes when
>> halting the process.
>>
>> /Dan
>>
>>
>
>
> This means that the implementation does not match the documentation. I think
> one or the other should change :-)
> Or the documentation writers have another understanding of the words "logged
> to disk" than I do :-)
> Sincerely,
> jw
>
>
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