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Message-ID: <4C33B509.5070403@gmail.com>
Date: Wed, 07 Jul 2010 00:58:17 +0200
From: Volker Mische <volker.mische@gmail.com>
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To: dev@couchdb.apache.org
CC: Mikeal Rogers <mikeal.rogers@gmail.com>,
 Damien Katz <damien@apache.org>
Subject: Re: delayed_commits false
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I have to admit that the point, that the main audience of a tarball are 
developers is a good one. Perhaps people that do binary distributions 
of CouchDB (like all the linux distros) could be encouraged to turn it 
to false (though I have no idea what their general policy about changing 
defaults is).

Cheers,
   Volker

On 07.07.2010 00:52, Mikeal Rogers wrote:
> I think there is a balance that we can find here between user experience and
> durability.
>
> I think the biggest question for me is, who is the primary target of the
> tarball download?
>
> If it's developers, I think we should leave it on.
>
> If it's people who are going to put it up, vanilla, in to production, we
> should turn them off.
>
> I know that I would certainly advocate keeping them off in the CouchDBX
> build.
>
> -Mikeal
>
> On Tue, Jul 6, 2010 at 3:46 PM, Volker Mische<volker.mische@gmail.com>wrote:
>
>> On 07.07.2010 00:06, Damien Katz wrote:
>>
>>>
>>> On Jul 5, 2010, at 8:49 AM, Volker Mische wrote:
>>>
>>>   Hi All,
>>>>
>>>> delayed_commits were enabled to have better performance especially for
>>>> single writers. The price you pay for is that you potentially lose up to one
>>>> second of writes in case of a crash.
>>>>
>>>> Such a setting makes sense, though in my opinion it shouldn't be enabled
>>>> by default. I expect* that people running into performance issues at least
>>>> take a look at the README or a FAQ section somewhere. There the
>>>> delayed_commit setting could be pointed out.
>>>>
>>>> I'd like to be able to say that on a vanilla CouchDB it's hard to lose
>>>> data, but I can't atm. I'm also well aware that there will be plenty of
>>>> performance tests when 1.0 is released and people will complain (if
>>>> delayed_commits would be set to false by default) that it is horrible slow.
>>>> Though safety of the data is more important for me.
>>>>
>>>> If the only reason why delayed_commits is true by default are the
>>>> performance tests of some noobs, I really don't think it's a price worth
>>>> paying.
>>>>
>>>> *I know that in reality people don't
>>>>
>>>> I would like to see delayed_commits=false for 1.0
>>>>
>>>
>>> Last year we turned off delayed commits by default. We got lots of
>>> complaints, the performance impact was too great. So we switched it back. We
>>> aren't the first storage engine to go around on this. For example, Apple's
>>> core data switched to using full fsyncs for each write in 10.4, but then
>>> switched it back for 10.5:
>>>
>>>
>>> http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CoreData/Articles/cdPersistentStores.html
>>>
>>> "Important: The default behaviors in Mac OS X v10.4 an 10.5 are different.
>>> In Mac OS X v10.4, SQLite uses FULL_FSYNC by default; in Mac OS X v10.5 it
>>> does not."
>>>
>>> Anyway, we can improve the documentation warning's, etc, but we should
>>> stay with the current defaults.
>>>
>>> -Damien
>>>
>>>
>> As 1.0 is approaching fast, I think this discussion is pretty important.
>> Especially this thread showed that there are people that prefer setting
>> delayed_commits to false. Although sometimes someone has to make the last
>> call, and there is probably no one better than the creator of the project, I
>> think it this case the decision should be made by more people.
>>
>> For *me personally* the authority of Apache CouchDB are the committers. I
>> would love to see them vote on this topic (being it public or private
>> doesn't matter).
>>
>> Cheers,
>>   Volker
>>
>