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From Furkan KAMACI <>
Subject Re: Approximately needed RAM for 5000 query/second at a Solr machine?
Date Wed, 10 Apr 2013 03:12:10 GMT
I am sorry but you said:

*you need enough free RAM for the OS to cache the maximum amount of disk
space all your indexes will ever use*

I have made an assumption my indexes at my machine. Let's assume that it is
5 GB. So it is better to have at least 5 GB RAM? OK, Solr will use RAM up
to how much I define it as a Java processes. When we think about the
indexes at storage and caching them at RAM by OS, is that what you talk
about: having more than 5 GB - or - 10 GB RAM for my machine?

2013/4/10 Shawn Heisey <>

> On 4/9/2013 7:03 PM, Furkan KAMACI wrote:
> > These are really good metrics for me:
> >
> > You say that RAM size should be at least index size, and it is better to
> > have a RAM size twice the index size (because of worst case scenario).
> >
> > On the other hand let's assume that I have a RAM size that is bigger than
> > twice of indexes at machine. Can Solr use that extra RAM or is it a
> > approximately maximum limit (to have twice size of indexes at machine)?
> What we have been discussing is the OS cache, which is memory that is
> not used by programs.  The OS uses that memory to make everything run
> faster.  The OS will instantly give that memory up if a program requests
> it.
> Solr is a java program, and java uses memory a little differently, so
> Solr most likely will NOT use more memory when it is available.
> In a "normal" directly executable program, memory can be allocated at
> any time, and given back to the system at any time.
> With Java, you tell it the maximum amount of memory the program is ever
> allowed to use.  Because of how memory is used inside Java, most
> long-running Java programs (like Solr) will allocate up to the
> configured maximum even if they don't really need that much memory.
> Most Java virtual machines will never give the memory back to the system
> even if it is not required.
> Thanks,
> Shawn

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