>> 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 <furkankam...@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 <s...@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
