In addition to Shawn's comments, you might want to see: http://blog.thetaphi.de/2012/07/use-lucenes-mmapdirectory-on-64bit.html
Lucene's use of MMapDirectory can mislead you when looking at memory usage.... Best Erick On Mon, Oct 29, 2012 at 5:59 PM, Shawn Heisey <s...@elyograg.org> wrote: > On 10/29/2012 3:26 PM, shreejay wrote: >> >> I am trying to run two SolrCloud with 3 and 2 shards respectively (lets >> say >> Cloud3shards and Clouds2Shards). All servers are identical with 18GB Ram >> (16GB assigned for Java). > > > This bit right here sets off warning bells right away. You're only leaving > 2GB of RAM for the OS to cache your index, which you later say is 50GB. > It's impossible for me to give you a precise figure, but I would expect that > with an index that size, you'd want to have at least 20GB of free memory, > and if you can have 50GB or more of free memory after the OS and Java take > their chunk, Solr would have truly excellent performance. As it is now, > your performance will be terrible, which probably explains all your issues. > > It seems highly unlikely that you would have queries complex enough that you > actually do need to allocate 16GB of RAM to Java. Also, requesting large > numbers of documents (the 5000 and 20000 numbers you mentioned) is slow, and > compounded in a cloud (distributed) index. Solr is optimized for a small > number of results. > > First recommendation for fixing things: get more memory. 32GB would be a > good starting point, 64GB would be better, so that the entire index will be > able to fit in OS cache memory. If you expect your index to grow at all, > plan accordingly. > > Second recommendation, whether or not you get more actual memory: Lower the > memory that Java is using, and configure some alternate memory management > options for Java. Solr does have caching capability, but it is highly > specialized. For general index caching, the OS does a far better job, and > it needs free memory in order to accomplish it. Here's some commandline > options for Java that I passed along to someone else on this list: > > -Xmx4096M -Xms4096M -XX:NewRatio=1 -XX:+UseParNewGC -XX:+UseConcMarkSweepGC > -XX:+CMSParallelRemarkEnabled > > http://www.petefreitag.com/articles/gctuning/ >
