Any sources to cite for this statement? And are you talking about RAM allocated to the JVM or available for OS cache?
> Not sure if this was mentioned yet, but if you are doing slave/master > replication you'll need 2x the RAM at replication time. Just something to > keep in mind. > > -mike > > On Mon, Jan 10, 2011 at 5:01 PM, Toke Eskildsen <t...@statsbiblioteket.dk>wrote: > > On Mon, 2011-01-10 at 21:43 +0100, Paul wrote: > > > > I see from your other messages that these indexes all live on the > > > > same > > > > machine. > > > > > > You're almost certainly I/O bound, because you don't have enough > > > > memory > > > > for the > > > > > > OS to cache your index files. With 100GB of total index size, you'll > > > > get best > > > > > > results with between 64GB and 128GB of total RAM. > > > > > > Is that a general rule of thumb? That it is best to have about the > > > same amount of RAM as the size of your index? > > > > I does not seems like there is a clear current consensus on hardware to > > handle IO problems. I am firmly in the SSD camp, but as you can see from > > the current thread, other people recommend RAM and/or extra machines. > > > > I can say that our tests with RAM and spinning disks showed us that a > > lot of RAM certainly helps a lot, but also that it takes a considerable > > amount of time to warm the index before the performance is satisfactory. > > It might be helped with disk cache tricks, such as copying the whole > > index to /dev/null before opening it in Solr. > > > > > So, with a 5GB index, I should have between 4GB and 8GB of RAM > > > dedicated to solr? > > > > Not as -Xmx, but free for disk cache, yes. If you follow the RAM ~= > > index size recommendation.
