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Re: fsync()-in webdav PUT

Valery Kholodkov
February 28, 2018 01:56PM
On 28-02-18 15:08, Maxim Dounin wrote:
>> What do you mean by a reliable server?
>> I want to make sure when the HTTP operation returns, the file is on the
>> disk, not just in a buffer waiting for an indefinite amount of time to
>> be flushed.
>> This is what fsync is for.
>
> The question here is - why you want the file to be on disk, and
> not just in a buffer? Because you expect the server to die in a
> few seconds without flushing the file to disk? How probable it
> is, compared to the probability of the disk to die? A more
> reliable server can make this probability negligible, hence the
> suggestion.

I think the point here is that lack of fsync leaves some questions
unanswered. Adding fsync will simply put all dots above the "i"s.

> (Also, another question is what "on the disk" meas from physical
> point of view. In many cases this in fact means "somewhere in the
> disk buffers", and a power outage can easily result in the file
> being not accessible even after fsync().)
>
>> Why doing this in a thread is not a good idea? It would'nt block nginx
>> that way.
>
> Because even in threads, fsync() is likely to cause performance
> degradation. It might be a better idea to let the OS manage
> buffers instead.

fsync does not cause performance degradation. fsync simply instructs OS
to ensure consistency of a file. What causes performance degradation is
expenditure of resources necessary to ensure consistency.

val
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Subject Author Posted

fsync()-in webdav PUT

Nagy, Attila February 27, 2018 05:24AM

Re: fsync()-in webdav PUT

Maxim Dounin February 27, 2018 08:26AM

Re: fsync()-in webdav PUT

Nagy, Attila February 28, 2018 04:32AM

Re: fsync()-in webdav PUT

Aziz Rozyev February 28, 2018 05:06AM

Re: fsync()-in webdav PUT

Valery Kholodkov February 28, 2018 01:26PM

Re: fsync()-in webdav PUT

Aziz Rozyev February 28, 2018 04:44PM

Re: fsync()-in webdav PUT

Aziz Rozyev February 28, 2018 05:08PM

Re: fsync()-in webdav PUT

pbooth February 28, 2018 05:36PM

Re: fsync()-in webdav PUT

Valery Kholodkov March 01, 2018 07:26AM

Re: fsync()-in webdav PUT

Valery Kholodkov March 01, 2018 07:30AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 04:02AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 05:04AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 03:52AM

Re: fsync()-in webdav PUT

Maxim Dounin February 28, 2018 09:10AM

Re: fsync()-in webdav PUT

Valery Kholodkov February 28, 2018 01:56PM

Re: fsync()-in webdav PUT

itpp2012 February 28, 2018 03:28PM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 04:14AM

Re: fsync()-in webdav PUT

Aziz Rozyev March 02, 2018 05:44AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 06:32AM

RE: fsync()-in webdav PUT

Reinis Rozitis March 04, 2018 07:42AM

Re: fsync()-in webdav PUT

Nagy, Attila March 05, 2018 05:32AM

RE: fsync()-in webdav PUT

Reinis Rozitis March 05, 2018 06:56AM

Re: fsync()-in webdav PUT

Valery Kholodkov March 05, 2018 08:14AM

Re: fsync()-in webdav PUT

Nagy, Attila March 05, 2018 08:56AM

Re: fsync()-in webdav PUT

Richard Demeny March 05, 2018 09:06AM

Re: fsync()-in webdav PUT

Maxim Dounin March 02, 2018 11:08AM

Re: fsync()-in webdav PUT

Valery Kholodkov March 02, 2018 02:50PM

Re: fsync()-in webdav PUT

Maxim Dounin March 02, 2018 07:44PM



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