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From "Chhabra, Kapil" <kchha...@akamai.com>
Subject RE: RAMDirectory vs FSDirectory
Date Tue, 27 Nov 2007 07:28:37 GMT
> one can improve search performance by using a RAMDirectory created
from an underlying FSDirectory using one of the parameterised
constructors. Is this correct?
Absolutly

> Will a FSDirectory not automatically load the index into memory
provided enough RAM is available?  
Not all index files are loaded in the RAM if you are using the
FSDirectory. Though at the same time, queries are cached.

> Do I have to explicitly use a RAMDirectory?
If you want to load the comeplte index in the memory, yes. This increase
the performance a lot as it drastically reduces the number of disk IO.
Obviously at the cost of the RAM. If you have enough RAM available to
accommodate the complete index, you can go ahead with this.

Regards,
kapilChhabra

-----Original Message-----
From: Hardy Ferentschik [mailto:hardy@ferentschik.de] 
Sent: Tuesday, November 27, 2007 12:25 PM
To: java-user@lucene.apache.org
Subject: RAMDirectory vs FSDirectory

Hi there,

I am using currently a FSDirectory to build my index. The reason for
using a file system based index is that a full index rebuild takes
around 30 minutes and I want to keep a persistent index.
In 'Lucene in Action' I've read that one can improve search performance
by using a RAMDirectory created from an underlying FSDirectory using one
of the parameterised constructors. Is this correct? Will a FSDirectory
not automatically load the index into memory provided enough RAM is
available?  
Do I have to explicitly use a RAMDirectory?

--Hardy

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