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From Rallavagu <rallav...@gmail.com>
Subject Re: Solr hard commit
Date Tue, 27 Oct 2015 04:07:05 GMT
Erick, Thanks for clarification. I was under impression that 
MMapDirectory is being used for both read/write operations. Now, I see 
how it is being used. Essentially, it only reads from MMapDirectory and 
writes directly to disk. So, the updated file(s) on the disk 
automatically read into memory as they are Memory mapped?

On 10/26/15 8:43 PM, Erick Erickson wrote:
> You're really looking at this backwards. The MMapDirectory stuff is
> for Solr (Lucene, really) _reading_ data from closed segment files.
>
> When indexing, there are internal memory structures that are flushed
> to disk on commit, but these have nothing to do with MMapDirectory.
>
> So the question is really moot ;)
>
> Best,
> Erick
>
> On Mon, Oct 26, 2015 at 5:47 PM, Rallavagu <rallavagu@gmail.com> wrote:
>> All,
>>
>> Are memory mapped files (mmap) flushed to disk during "hard commit"? If yes,
>> should we disable OS level (Linux for example) memory mapped flush?
>>
>> I am referring to following for mmap files for Lucene/Solr
>>
>> http://blog.thetaphi.de/2012/07/use-lucenes-mmapdirectory-on-64bit.html
>>
>> Linux level flush
>>
>> http://www.cyberciti.biz/faq/linux-stop-flushing-of-mmaped-pages-to-disk/
>>
>> Solr's hard and soft commit
>>
>> https://lucidworks.com/blog/2013/08/23/understanding-transaction-logs-softcommit-and-commit-in-sorlcloud/
>>
>> Thanks in advance.

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