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From Cheng <zhoucheng2...@gmail.com>
Subject Re: Configure writer to write to FSDirectory?
Date Sun, 05 Feb 2012 14:03:58 GMT
Hi Uwe,

My challenge is that I need to update/modify the indexes frequently while
providing the search capability. I was trying to use FSDirectory, but found
out that the reading and writing from/to FSDirectory is unbearably slow. So
I now am trying the RAMDirectory, which is fast.

I don't know of  MMapDirectory, and wonder if it is as fast as RAMDirectory.


On Sun, Feb 5, 2012 at 4:14 PM, Uwe Schindler <uwe@thetaphi.de> wrote:

> Hi Cheng,
>
> It seems that you use a RAMDirectory for *caching*, otherwise it makes no
> sense to write changes back. In recent Lucene versions, this is not a good
> idea, especially for large indexes (RAMDirectory eats your heap space,
> allocates millions of small byte[] arrays,...). If you need something like
> a
> caching Directory and you are working on a 64bit platform, you can use
> MMapDirectory (where the operating system kernel manages the read/write
> between disk an memory). MMapDirectory is returned by default for
> FSDirectory.open() on most 64 bit platforms. The good thing: the "caching"
> space is outside your JVM heap, so does not slowdown the garbage collector.
> So be sure to *not* allocate too much heap space (-Xmx) to your search app,
> only the minimum needed to execute it and leave the rest of your RAM
> available for the OS kernel to manage FS cache.
>
> Uwe
>
> -----
> Uwe Schindler
> H.-H.-Meier-Allee 63, D-28213 Bremen
> http://www.thetaphi.de
> eMail: uwe@thetaphi.de
>
>
> > -----Original Message-----
> > From: Cheng [mailto:zhoucheng2008@gmail.com]
> > Sent: Sunday, February 05, 2012 7:56 AM
> > To: java-user@lucene.apache.org
> > Subject: Configure writer to write to FSDirectory?
> >
> > Hi,
> >
> > I build an RAMDirectory on a FSDirectory, and would like the writer
> associated
> > with the RAMDirectory to periodically write to hard drive.
> >
> > Is this achievable?
> >
> > Thanks.
>
>
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>

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