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From Ravi Prakash <ravihad...@gmail.com>
Subject Re: About HDFS consistency model
Date Mon, 31 Jul 2017 20:09:34 GMT
Hi Hongxu!

It might be best to go through JIRA comments. Some of them have design docs
too. e.g. https://issues.apache.org/jira/browse/HDFS-265 ,
https://issues.apache.org/jira/browse/HDFS-744 etc.

I know there may be some windy conversations, but the good thing about
open-source is that all these deliberations are for everyone to see.


On Mon, Jul 31, 2017 at 3:13 AM, Hongxu Ma <interma@outlook.com> wrote:

> Hi Dev
> In short, is there a full introduction to hdfs consistency model?
> I have already read some miscellaneous stuffs, e.g.
> - some simple scenario
>     - read+read, ok
>     - write+write, forbidden (guaranteed be lease)
> - design doc of append, truncate
> - hflush/hsync
> - top pages of google "hdfs consistency model"
> But I didn't find a detailed doc/link to clarify this topic, especially
> how to deal with concurrent read+write, e.g.:
> Can a later reader can read the contents which the writer (doesn't close
> the file yet) appended? Is hflush/hsync the only ways to ensure the
> consistency? etc..
> I known the GFS paper has a specific section to clarify this topic, so I
> think hdfs may has a similar one.
> Very thanks for helpful link.
> --
> Regards,
> Hongxu.

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