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From Furkan KAMACI <furkankam...@gmail.com>
Subject Re: Approximately needed RAM for 5000 query/second at a Solr machine?
Date Thu, 11 Apr 2013 06:44:18 GMT
Hi Walter;

Is there any document or something else says that worst case is three times
of disk space? Twice times or three times. It is really different when we
talk about GB's of disk spaces.


2013/4/10 Walter Underwood <wunder@wunderwood.org>

> Correct, except the worst case maximum for disk space is three times.
> --wunder
>
> On Apr 10, 2013, at 6:04 AM, Erick Erickson wrote:
>
> > You're mixing up disk and RAM requirements when you talk
> > about having twice the disk size. Solr does _NOT_ require
> > twice the index size of RAM to optimize, it requires twice
> > the size on _DISK_.
> >
> > In terms of RAM requirements, you need to create an index,
> > run realistic queries at the installation and measure.
> >
> > Best
> > Erick
> >
> > On Tue, Apr 9, 2013 at 10:32 PM, bigjust <bigjust@lambdaphil.es> wrote:
> >>
> >>
> >>
> >>>> 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
> >>>>
> >>>>
> >> Furkan KAMACI <furkankamaci@gmail.com> writes:
> >>
> >>> 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 <solr@elyograg.org>
> >>>
> >>
> >> 10 GB.  Because when Solr shuffles the data around, it could use up to
> >> twice the size of the index in order to optimize the index on disk.
> >>
> >> -- Justin
>
> --
> Walter Underwood
> wunder@wunderwood.org
>
>
>
>

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