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From Damien Katz <dam...@apache.org>
Subject Re: delayed_commits false
Date Tue, 06 Jul 2010 23:03:04 GMT
This issue has been discussed already. A change this big right before a 1.0 release is a very
bad idea. If we decided to change it, we'd need to wait a good amount of time to understand
how it affects downstream projects that take the defaults.

Here is a bug report that talks about it. There is more discussion in the mailing list as
well.

https://issues.apache.org/jira/browse/COUCHDB-449

-Damien


On Jul 6, 2010, at 3:58 PM, Volker Mische wrote:

> 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
>>> 
>> 
> 


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