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From Dawid Weiss <dawid.we...@gmail.com>
Subject Re: RAM or SSD...
Date Thu, 19 Jul 2012 11:34:26 GMT
Read this:
http://blog.thetaphi.de/2012/07/use-lucenes-mmapdirectory-on-64bit.html

Dawid

On Thu, Jul 19, 2012 at 1:32 PM, Dragon Fly <dragon-fly999@hotmail.com> wrote:
>
> The slowest part of my application is to read the search hits from disk.  I was hoping
that using an SSD or RAMDirectory/MMapDirectory would speed that up.  I read the JavaDoc for
MMapDirectory but didn't really understand how that differs from RAMDirectory.  Could someone
please explain?
>
>> Date: Wed, 18 Jul 2012 23:46:51 -0700
>> Subject: Re: RAM or SSD...
>> From: vfunstein@gmail.com
>> To: java-user@lucene.apache.org
>>
>> I was referring to *RAMDirectory*.
>>
>> On Wed, Jul 18, 2012 at 11:04 PM, Lance Norskog <goksron@gmail.com> wrote:
>> >> You do not want to store 30 G of data in the JVM heap, no matter what
>> library does this.
>> > MMapDirectory does not store data in the JVM heap. It lets the
>> > operating system manage the disk buffer space. Even if the JVM says "I
>> > have 30G of memory space", it really does not. It only has address
>> > space allocated by the  OS but no memory.
>> >
>> > On Wed, Jul 18, 2012 at 10:39 PM, Toke Eskildsen <te@statsbiblioteket.dk>
>> wrote:
>> >> On Wed, 2012-07-18 at 17:50 +0200, Dragon Fly wrote:
>> >>> If I want to improve performance, which of the following is better and
>> why?
>> >>>
>> >>> 1. Buy a machine with a lot of RAM and use a RAMDirectory for the index.
>> >>
>> >> As others has pointed out, MMapDirectory should work better than
>> >> RAMDirectory. I am sure it will work fine with a relative small index
>> >> such as yours. However, it does not scale that well with index size.
>> >>
>> >>> 2. Put the index on a solid state drive.
>> >>
>> >> Why anyone buys computers without SSD's is a mystery to me. Use SSDs for
>> >> the small low-latency stuff and a secondary spinning drive for the large
>> >> slow stuff. Nowadays, a 30GB index (or 100GB for that matter) falls into
>> >> the small low-latency bucket. SSDs speeds up almost everything, saves
>> >> RAM and spares a lot of work hours optimizing I/O-speed.
>> >>
>> >> Regards,
>> >> Toke Eskildsen
>> >>
>> >>
>> >> ---------------------------------------------------------------------
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>> >>
>> >
>> >
>> >
>> > --
>> > Lance Norskog
>> > goksron@gmail.com
>> >
>> > ---------------------------------------------------------------------
>> > To unsubscribe, e-mail: java-user-unsubscribe@lucene.apache.org
>> > For additional commands, e-mail: java-user-help@lucene.apache.org
>> >
>

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