On Mon, 2015-11-02 at 16:25 +0530, Modassar Ather wrote: > The remaining size after you removed the heap usage should be reserved for > the index (not only the other system activities). > I am not able to get the above point. So when I start Solr with 28g RAM, > for all the activities related to Solr it should not go beyond 28g. And the > remaining heap will be used for activities other than Solr. Please help me > understand.
It is described here: https://wiki.apache.org/solr/SolrPerformanceProblems#OS_Disk_Cache I will be quick to add that I do not agree with Shawn (the primary author of the page) on the stated limits and find that the page in general ignores that performance requirements differ a great deal. Nevertheless, it is very true that Solr performance is tied to the amount of OS disk cache: You can have a machine with 10TB of RAM, but Solr performance will still be poor if you use it all for JVMs. Practically all modern operating system uses free memory for disk cache. Free memory is the memory not used for JVMs or other programs. It might be that you have a lot less than 30-40GB free: If you are on a Linux server, try calling 'top' and see what is says under 'cached'. Related, I support jim's suggestion to inspect the swap activity: In the past we had problem with a machine that insisted on swapping excessively, although there were high IO and free memory. > The disks are SSDs. That makes your observations stranger still. - Toke Eskildsen, State and University Library, Denmark
