On 9/11/2013 4:16 PM, Deepak Konidena wrote:
As far as RAM usage goes, I believe we set the heap size to about 40% of the RAM and less than 10% is available for OS caching ( since replica takes another 40%). Why does unallocated RAM help? How does it impact performance under load?
Because once the data is in the OS disk cache, reading it becomes instantaneous, it doesn't need to go out to the disk. Disks are glacial compared to RAM. Even SSD has a far slower response time. Any recent operating system does this automatically, including the one from Redmond that we all love to hate.
http://blog.thetaphi.de/2012/07/use-lucenes-mmapdirectory-on-64bit.html Thanks, Shawn
