Theres a bit to it, sometimes it can use tweaking though. Its a good default for most systems so I wouldn't increase right off the bat. When using ssds or something with a lot of horsepower it could be higher though (ie i2.xlarge+ on ec2). If you monitor the number of active threads in read thread pool (nodetool tpstats) you can see if they are actually all busy or not. If its near 32 (or whatever you set it at) all the time it may be a bottleneck.
--- Chris Lohfink On Wed, Oct 29, 2014 at 10:41 PM, Jimmy Lin <y2klyf+w...@gmail.com> wrote: > Hi, > looking at the docs, the default value for concurrent_reads is 32, which > seems bit small to me (comparing to say http server)? because if my node is > receiving slight traffic, any more than 32 concurrent read query will have > to wait.(?) > > Recommend rule is, 16* number of drives. Would that be different if I have > SSDs? > > I am attempting to increase it because I have a few tables have wide rows > that app will fetch them, the pure size of data may already eating up the > thread time, which can cause other read threads need to wait and essential > slow. > > thanks > > > >
